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Yr 2 - Research methods > Definitions > Flashcards

Definitions Flashcards

1
Q

What is Accuracy?

A

How close the sample statistic is on average to the population parameter that it estimates

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2
Q

What is age standardisation?

A

Adjustment to minimise the effects of differences in age composition, when comparing summary statistics across different populations

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3
Q

What is ANOVA?

A

(Analysis of Variance) = A statistical test used to compare means in three or more groups (one way for unmatched data and repeated measures for matched data)

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4
Q

What is a bar chart?

A

A graph used to present a categorical variable; frequencies within each group of observations are represented by the heights of the corresponding bars

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5
Q

What is a baseline/reference group?

A

The group (usually the unexposed group) with which other exposure groups are compared

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6
Q

What is bias?

A

Systematic departure from the true value which can give misleading results; includes selection, loss to follow up, measurement (recall and interviewer) and performance bias

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7
Q

What is a binary variable/ dichotomous?

A

A categorical variable which can only take one of two values

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8
Q

What is blinding?

A

Subjects and/or outcome assessors are unaware of treatment allocation in a randomised controlled trial

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9
Q

What is a box and whisker plot?

A

A graph used to present a continuous outcome by a categorical exposure; boxes for each category represent medians and inter-quartile ranges and whiskers represent the extreme values for the outcome

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10
Q

What are case-control studies?

A

Study designed such that subjects are recruited on the basis of the presence (case) or absence (control) of an outcome, then an exposure is measured retrospectively

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11
Q

What is a categorical variable?

A

Values indicated category membership; can be ordinal or nominal

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12
Q

What is a causal factor?

A

Exposure which causes an outcome i.e. must precede the outcome

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13
Q

What is central tendency?

A

Location of a distribution including mean, median and mode

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14
Q

What is chance?

A

Variation that is due to random fluctuations

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15
Q

What is the chi-squared test?

A

Statistical test used to compare two unmatched continuous variables; an ordinal version also exists

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16
Q

What is clinical equipoise?

A

A state of uncertainty where it is believed to be equally likely that either of two treatment options may be better

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17
Q

What is the clinical iceberg?

A

Phenomenon whereby health practitioners are only aware of the relatively small proportion of diseases that present to them

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18
Q

What is the cochrane Q test?

A

Statistical test used to compare two categorical variables when data are matched

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19
Q

What is a cohort study?

A

(also known as longitudinal or follow up study) = Participants are identified as a sample from a population, then collection of exposure and outcome data depends on whether the study of prospective or historical

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20
Q

What is concealment?

A

Random allocation is hidden from investigators in randomised controlled trials making it impossible for them to have any influence over allocation of participants in treatment groups

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21
Q

What is a confidence interval?

A

Interval with a given probability (i.e. 95%) that it contains the true value of a population parameter, measures the precision of the sample statistic

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22
Q

What is a confounder?

A

A third variable which provides an alternative explanation for the observed association between an exposure and outcome

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23
Q

What is confounding?

A

Association with a third variable which provides an alternative explanation for the observed association between an exposure and outcome

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24
Q

What is confounding?

A

Association with a third variable which provides an alternative explanation for the observed association between an exposure and outcome

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25
Q

What is a contingency table?

A

Table showing the frequencies of observations for two categorical variables such that sub-categories of one variable (exposure) are indicated in rows and sub-categories of the other variable (outcome) are indicated in columns

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26
Q

What is a continuous variable?

A

A numerical variable which can potentially take an infinite number of distinct values

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27
Q

What is a correlation coefficient?

A

Measure of association that indicates the degree to which variable change together; can be pearsons (parametric) or spearman (non parametric)

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28
Q

What is critical appraisal?

A

Judgement made as to the quality of published articles e.g. regarding whether the appropriate study design and statistical methods have been chosen

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29
Q

What is a cross sectional study?

A

Study that examines the association between exposure and outcome at a particular point in time

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30
Q

Wat is a crude association?

A

Also known as an unadjusted association. Estimated association between exposure and outcome, before possible confounding variables are taken into account

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31
Q

What is a crude association?

A

Also known as an unadjusted association. Estimated association between exposure and outcome, before possible confounding variables are taken into account

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32
Q

What is demography?

A

Study of populations, especially with reference to size, density, morality, fertility, growth, age distribution and the interaction of these with social and economic factors

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33
Q

What is denominator?

A

The lower portion of a fraction used to calculate a rate or ratio

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34
Q

What is a descriptive study?

A

A study concerned with describing a variable in terms of time, place or person

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35
Q

What is detection bias?

A

Form of measurement bias that may occur when the outcome assessor is not blinded

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36
Q

What is a diagnostics test?

A

A test performed to aid diagnosis of an outcome (usually a disease), often compared with a gold standard in reliability studies

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37
Q

What is a discrete variable?

A

A numerical value representing counts, which cannot take on any intermediate values

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38
Q

What is the dose-response effect/trend?

A

Pattern of association observed between exposure (does) and outcome (response) including linear trend and threshold effects

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39
Q

What is ecological fallacy?

A

Bias that may occur because an association observed between variables on an aggregate level does not necessarily represent the association that exists at an individual level

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40
Q

What is an ecological study?

A

Study in which the unit of analysis is populations or groups of people, rather than individuals

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41
Q

What is eligibility criteria?

A

The criteria that must be met by subjects eligible for inclusion in a study

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42
Q

What is epidemiology?

A

Study of the distribution and determinants of health-related conditions or events in specified populations and the application of this study to the control of health problems

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43
Q

What is ethical approval?

A

Approval that must be sought from a local or regional ethics committee before a randomised controlled trial can be undertaken

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44
Q

What is Evidence-based healthcare?

A

The conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients

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45
Q

What is exposure/ explanatory variable/ independent variable/ x-variable/ risk factor/treatment group/intervention group?

A

A variable whose influence on the outcome variable is of interest

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46
Q

What os fisher’s exact test?

A

Statistical test used to compare two unpaired dichotomous variables in small datasets

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47
Q

What is Friedman test?

A

A statistical test used to compare distributions between three or more groups, when variables are matched and not normally distributed

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48
Q

What is the geometric mean?

A

A back transformation (antilog/exponential) of a mean value which has been calculated on logged data

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49
Q

What is a gold standard?

A

Measurement method widely accepted as being the best available, often used in reliability studies

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50
Q

What is a gold standard?

A

Measurement method widely accepted as being the best available, often used in reliability studies

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51
Q

What is the hierachy of evidence?

A

Simple guide to assessment of the evidence provided by different study designs randomised controlled trials (highest level) -> cohort -> case-control -> cross-sectional -> ecological -> descriptive; although quality of evidence also depends on quality of the study design and execution

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52
Q

What is a histogram?

A

Graphical representation of the frequency distribution of a continuous variable with areas of the bars representing the frequencies within each grouping interval

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53
Q

What is a historical/retrospective cohort study?

A

Outcome status for a defined sunset of the populations i ascertained at baseline and then linked to pre-existing historical data on exposure usually from routine records, so that the cohort’s experience of outcome risk can be reconstructed

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54
Q

What is a hypothesis?

A

Idea expressed in such a way that it can be tested and refuted

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55
Q

What is hypothesis testing?

A

Statistical methods used to determine how likely observed differences in data are due to chance rather than real differences

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56
Q

What is incident rate?

A

Rate of occurrence of new cases of an outcome, which is dependent on the number of new cases, total number in the population, and the time interval of interest

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57
Q

What is (statistical) interference?

A

Drawing conclusions abut some unknown aspect of a population, based on statistics derived from a random sample from that population

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58
Q

What is informed consent?

A

Consent five by the subject or responsible person fro participation in a study - usually randomised controlled trial

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59
Q

What is intention to treat analysis?

A

Participants in a randomised controlled trial analysed according to their treatment group allocation, regardless of whether they completed the trial

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60
Q

What is interaction?

A

An interaction between an exposure and confounder exists if the association between an outcome and exposure varies across the categories of the confounding variable

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61
Q

What is an intercept?

A

Point where a linear regression line crosses the y-axis i.e. value of the outcome when the exposure is zero

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62
Q

What is an inter-quartile range?

A

A measure of variability = the spread of data around the median, and is the distance between the lower quartile (25th gentile) value and at the upper quartile (75th centile) of a distribution

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63
Q

What is an interventional study?

A

A study where an investigator tests whether modifying or changing something (‘intervening’) alters the outcome, usually a randomised controlled trial or experimental study

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64
Q

What is interviewer bias?

A

Form of measurement bias where an interviewer inquires more deeply about exposure in those with the outcome compared to those without

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65
Q

What is kappa?

A

Measures the agreement between two or more examiners or methods when the variables are both categorial; if one or more of the variables are ordinal a modified version called the weighted kappa should be used

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66
Q

What is Kruskal-Wallis test?

A

A statistical test used to compare distributions between three or more groups when variables are unmatched and not normally distributed

67
Q

What are limits of agreement/bland altman method?

A

Gives an indication of the agreement between two examiners or methods when the variables are unmatched and not normally distributed

68
Q

What is linear regression?

A

Regression method appropriate for continuous outcomes that are approximately normally distributed, which produces regression coefficients

69
Q

What is the linear regression equation?

A

Equation derived from fitting a linear regression model, usually denoted y = a + bx

70
Q

What is a linear regression line?

A

A diagrammatic presentation (usually overlaid on a scatter plot) of a linear regression equation

71
Q

What is a linear trend?

A

A type of dose-response effect wherby there is a systematic increase in the risk of outcome with increasing or decreasing level of exposure

72
Q

What is logarithmic transformation?

A

Conversion of data to their natural log values, with the aim of achieving an approximate normal distribution

73
Q

What is a logistic regression?

A

Regression method appropriate for binary outcomes where the resulting regression coefficients can be exponentiated to produce odds ratios, multinomial and ordinal versions also exist

74
Q

What is a loss to follow up bias?

A

Bias due to subjects being lost over a follow up period, where the loss may be associated with the exposure and/or outcome

75
Q

What is the Mann Whitney U/ Wilcoxon signed rank test?

A

Statistical test used to compare distributions between two groups, when variables are unpaired and not normally distributed

76
Q

What is matched data?

A

Data that are not independent, often repeated measurements on the same person, or measurements from people who are related such as siblings or twins

77
Q

What is the McNemar’s test?

A

Statistical test used to compare two paired dichotomous variables

78
Q

What is a mean/average/arithmetic mean?

A

Measure of the central tendency calculated by summing all values and dividing by the total number of observations

79
Q

What is a mean/average/arithmetic mean?

A

Measure of the central tendency calculated by summing all values and dividing by the total number of observations

80
Q

What is measurement bias?

A

Bias in how the exposure and/or outcome is measured or classified that results in different quality of information collected between those with and without the outcome; includes detection, interviewer & recall bias

81
Q

What is a median?

A

Measure of central tendency, which is calculated as middle value when all the values are arranged in order, useful for summarising data that are not normally distributed

82
Q

What is mendelian randomisation?

A

Use of observational studies to obtain an estimate of the causal effect of a modifiable exposure on an outcome, through identification of a candidate gene which is related to exposure

83
Q

What is meta analysis?

A

Statistical technique for combining estimates of exposure-outcome associations from more than one study, weighting according to size of the study

84
Q

What is mode?

A

Measure of central tendency which is calculated as the most frequently occurring of all values, but is rarely used in epidemiology

85
Q

What is Multiple regression?

A

regression modelling when there is more than one exposure, or there is one exposure plus a number of confounders

86
Q

What is a nominal variable?

A

Unordered categorical variable i.e. categories have no order to them

87
Q

What are non-parametric/ distribution free methods?

A

Set of tests based on ranking observations in order of magnitude and testing these rankings rather than the actual values if the observations, suitable for data which are not normally distributed

88
Q

What is normal?

A 
Statistically = data follows a normal distribution;
Clinically = the likely values for an individual
89
Q

What is Normal distribution?

A

Continuous symmetrical frequency distribution where both tails extend to infinity and the shape is determined by the mean and standard deviation

90
Q

What is a null hypothesis?

A

Hypothesis that there is no association between outcome and exposure

91
Q

What is a numerator?

A

The upper portion of a fraction used to calculate a rate or ratio

92
Q

What is a numerical variable?

A

Values are numbers as opposed to categories

93
Q

What is an observational study?

A

Study that does not involve any form of intervention, where the investigatory just observes and records exposure and outcome information

94
Q

What are odds?

A

Number of people with thoutcome divided by the number of healthy people

95
Q

What is an odds ratio?

A

Ratio of odds of outcome amongst exposed subjects to the odds of outcome amongst unexposed subjects

96
Q

What are odds?

A

Number of people with the outcome divided by the number of healthy people

97
Q

What is an odds ratio?

A

Ratio of odds of outcome amongst exposed subjects to the odds of outcome amongst unexposed subjects

98
Q

What is an ordinal variable?

A

An ordered categorical variable i.e. categories can take values that are ranked according to an ordered classification

99
Q

What is an outcome?

A

(response variable/dependent variable/y-variable/cas-control status/disease group) = variable whose association with an exposure is of interest

100
Q

What is an outcome?

A

(response variable/dependent variable/y-variable/cas-control status/disease group) = variable whose association with an exposure is of interest

101
Q

What is paired data?

A

Special case of matched date when there are only two groups

102
Q

What is a parameter?

A

Numerical quantity measuring some aspect of a population e.g. the mean

103
Q

What are parametric methods?

A

Assume the data has an underlying distribution

104
Q

What is performance bias?

A

Bias arising due to an unequal provision of care between the treatment and control group in a randomised controlled trial, which may occur if subjects and assessors are not blinded

105
Q

What is per-protocol analysis/on treatment analysis?

A

Analysis restricted to those who completed a randomised controlled trial according to protocol, which defeats the main purpose of random allocation and may invalidate the results; it is preferable to use intention to treat analysis

106
Q

What is person-years at risk?

A

Sum of the number of years that each individual has been under observation, sometimes used as a denominator for calculating incidence rates

107
Q

What is a Pie chart?

A

Graph used to respresent a categorical variable; frequencies within each group of observations are represented by the areas of segments in a circular diagram

108
Q

What is a Placebo?

A

Inert medication or procedure i.e. a drug having no pharmacological effect, but intended to give patients the perception that they are receiving treatment for their complaint

109
Q

What is the placebo effect?

A

Phenomenon whereby a patients symptoms can be alleviated by an otherwise ineffective treatment, as they expect the treatment to work

110
Q

What is a Placebo group/control group?

A

Group of patients in a randomised controlled trial who receive no treatment other than standard care i.e.e placebo

111
Q

What is poisson regression?

A

Regression method appropriate for outcomes that are count variables; the resulting regression coefficients are usually exponentiated to produce rate ratios

112
Q

What is power?

A

Ability of a study to demonstrate an association between variables if one exists i.e. the probability of observing evidence against the null hypothesis if it is false

113
Q

What is precision?

A

Amount of variation in the sample statistic, with greater variation indicating less precision

114
Q

What is prevalence?

A

Total number of individuals who have an outcome at a particular time divided by the total population at risk at that time i.e. proportion with outcome at a particular time

115
Q

What s proportion?

A

Number of occurrences of an event divided by total number of observations

116
Q

What is a prospective cohort study?

A

Healthy individuals are recruited (though some may already have the outcome at baseline), exposure status recorded, then subjects are followed up to see whether those who were exposed develop the outcome at a different rate to those who were not exposed

117
Q

What is publication bias?

A

Tendency for studies that find associations between variables to get published, and the that do not find associations not to get published

118
Q

What is a P-value?

A

Probability that the difference between exposure groups would be at least as big as that observed if the null hypothesis of no difference is true i.e. if the difference has arisen due to chance

119
Q

What is R squared?

A

Proportion of variance in one variable that is explained by the variation in another, given by the square of the correlation coefficient (R)

120
Q

What is a random sample?

A

Sample drawn from a population such that all members of the population have an equal chance of being chosen

121
Q

What is randomisation?

A

(/random allocation) In randomised controlled trials, allocation of subjects in either the intervention or control group, by chance aloe, to ensure that groups are similar with respect to the distribution of confounding factors

122
Q

What is a randomised controlled trial?

A

Study in which subjects are randomly allocated to either a treatment or control group, followed up, then outcomes measured and compared

123
Q

What is range?

A

Measured variability which is the difference between the largest and smallest values in a distribution

124
Q

What is Rate?

A

measure of the frequency of occurrence of an event e.g. incidence rate

125
Q

What is rate ratio?

A

Quantification of the association between an exposure and discrete/count outcome, calculated using poisson regression models

126
Q

What is recall bias?

A

Form of measurement bias occurring in retrospective studies, whereby recall of information is different in the with the outcome compared to those without

127
Q

What is a reference range?

A

Measure of variability which indicates the amount of variation between individual observations in a sample and hence likely values for an individual in the population/can inform as to whether a patient is “clinically” normal.

128
Q

What is regression/regression modelling?

A

Finds the best mathematical model to describe the outcome (y) with respect to the exposure (x)

129
Q

What is regression coefficient?

A

(/slope) = Estimate of the change in outcome (y) for a unit change in exposure (x); in a linear regression this is the gradient of the linear regression line, denoted by b in the linear regression equation (y= a + bx)

130
Q

What is a reliability/inter-observer study?

A

Compares the measurements made by two or more examiners or methods with respect to the agreement between them

131
Q

What is reverse causality?

A

Alternative explanation for an exposure-outcome association, whereby the outcome causes the exposure rather than the other way around

132
Q

What is risk/incidence/cumulative incidence?

A

Number of new cases with he outcome in a particular time period divided by the number of people who did not have the outcome at the outset i.e. proportion of new cases in a time period

133
Q

What is risk difference?

A

Difference in risk between exposed and non-exposed groups

134
Q

What is a risk ratio/relative risk?

A

Risk of developing the outcome in the exposed group compared to risk of developing the outcome in the unexposed group

135
Q

What is sample size calculation/power calculation?

A

Mathematical process of deciding how many subjects should be included in a study, to be determined at the outset

136
Q

What is a sample statistic?

A

Estimate of a population parameter, based on a sample drawn from that popultion

137
Q

What is sampling?

A

Process of selecting a number of subjects from all the subjects in the target population

138
Q

What is sampling distribution?

A

Distribution of sample statistics if repeated samples were drawn from the same population

139
Q

What is a scatter plot?

A

Graph used to present two continuous variables, whereby each point represents the exposure and outcome values for an individual

140
Q

What is a selected sample?

A

Randoms ample of individuals that have been selected from the target population

141
Q

What is selection bias?

A

Systematic difference in the characteristics of the subjects selected randomly to take part in a study and those who are not

142
Q

What is sensitivity?

A

Proportion of sample with the outcome, who are correctly classified by a diagnostic test that has been compared to a gold standard (e.g. in reliability study)

143
Q

What is a sign test/ Wilcoxon signed rank test?

A

Statistical test used to compare distributions between two groups, when variables are paired but not normally distributed

144
Q

What is skewed?

A

An asymmetrical frequency distribution, which is either positively skewed (long tail to the right) or negatively skewed (long tail to the left)

145
Q

What is Specifity?

A

Proportion of sample without the outcome, who are correctly classified by a diagnostic test that has been compared to a gold standard (reliability study)

146
Q

What is standard deviation?

A

Measure of variability, indicating how widely dispersed the individual observations are in a distribution

147
Q

What is standard error?

A

Measurement of the precision of the sample mean as an estimate of the population mean standard deviation of the sampling distribution of a sample statistic

148
Q

What is a standard normal distribution?

A

Special case of the normal distribution where the mean is zero and the standard deviation is one

149
Q

What is statistical significance?

A

A p-value less than a specified level, usually 5%, suggesting that the null hypothesis can be rejected; although statistical results have traditionallyy been interpreted in this way it is now considered preferable to avoid the the term statistical significance!

150
Q

What are statistics?

A

Science of collecting, summarising, analysing (e.g. estimating the strength of association between two variables) and interpreting data

151
Q

What is a stratified analysis?

A

Analysis undertaken separately in each of a number of subgroups

152
Q

What is a study sample?

A

Subgroup of subjects from the selected sample that actually agree to take part in the study

153
Q

What is a subgroup?

A

Subdivision of the sample into groups

154
Q

What is survival analysis?

A

Statistical modelling of the time to an event which does not assume that rates are constant over time

155
Q

What is a systematic review?

A

Review of a clearly formulated question that uses systematic methods to identify, select and critically appraise relevant research

156
Q

What is a target population?

A

Collection of individuals for which it is of interest to draw inferences or be able to generalise too, often defined in terms of geographical location

157
Q

What is temporal?

A

Referring to time

158
Q

What is a test statistic?

A

Quantity calculated from the data which is used to assess the strength of evidence against the null hypothesis

159
Q

What is the threshold effect?

A

Type of dose-response effect, whereby the risk of the outcome is only increased in subjects whose exposure is above or below a certain level

160
Q

What is a t-test?

A

A statistical test used to compare means between two groups, when variables are approximately normally distributed; can be unpaired or paired test

161
Q

What is variability?

A

Measure of variability, the variance is the square of the standard deviation

162
Q

What is the Wilcoxon signed rank test?

A

The same as the Mann-Whitney U test for two unpaired groups & sign test for two paired groups

163
Q

What is a z-test?

A

Statistical test used to compare means between two groups, when variables are approximately normally distributed, and sample is not too small

Yr 2 - Research methods (11 decks)

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