Glossary Terms

Question 1

hypothesis stating that there is no difference between the study groups

Answer 1

null hypothesis

Question 2

probability that a difference between study groups would have occurred if the null hypothesis was true

Answer 2

P value

Question 3

range in which we can be approximately 95% certain that the population value lies

Answer 3

95% confidence interval

Question 4

When the null hypothesis is incorrectly rejected; a difference between groups is statistically significant although a clinically important difference exists
alpha error; false positive

Answer 4

Type I Error

Question 5

When the null hypothesis is incorrectly accepted; a difference between groups is not statistically significant although a clinically important difference exists

Answer 5

Type II Error

Question 6

number of new cases of a condition that develop in a population during a defined time period (cases/year)

Answer 6

incidence

Question 7

total number of people in a population with a condition during a given point in time (cases at birth)

Answer 7

prevalence

Question 8

statistic used to test whether the rate of an outcome is significant;y different between two or more exposure groups.
This test provides a probability that the outcome and exposure are independent

Answer 8

Chi-Square test

Question 9

statistic used to test whether there is a linear trend for an outcome to increase or decrease over the range of an ordered categorial exposure variable

Answer 9

Chi-Square test for trend

Question 10

the probability of an event or outcome occuring - such as infection, death, cure

Answer 10

risk

Question 11

ratio of the probability of the outcome occurring in the exposed group, divided by the probability of the outcome occurring in the non-exposed group

Answer 11

relative risk

Question 12

the probability of an event (p) occurring divided by the probability of that event not occurring (1-p)

Answer 12

odds

Question 13

radio of the odds of the outcome occuring in one group divided by the odds of the outcome occurring in another group

Answer 13

odds ratio

Question 14

initial trial of a new treatment to assess SAFETY and feasibility in a small group of volunteers who do not have the disease or patients with symptoms

Answer 14

Phase I Trial

Question 15

clinical trial to measure EFFICACY - the effect of treatment under ideal conditions in patients with the disease

Answer 15

Phase II Trial

Question 16

large randomized control trial or multi-center study to measure EFFECTIVENESS in the community - the effect of treatment in GENERAL CLINICAL PRACTICE

Answer 16

Phase III Trial

Question 17

POST MARKETING survery to measure rare adverse events

Answer 17

Phase IV Surveillance

Question 18

All participants are analyzed in the group to which they were allocated, regardless or subsequent events such as non-complicance or withdrawal from the study. This provides a conservative estimate of treatment effect that is not influenced by cofounders

Answer 18

Intention-to-Treat analysis

Question 19

only participants with final study outcomes are included in the data analysis but participants are maintained in the group to which they were allocated - results may be influenced by bias and cofounders

Answer 19

Available-case analysis

Question 20

participants are re-grouped according to the treatment they actually received, irrespective to te treatment to which they were allocated - by using this method there is no control of cofounders

Answer 20

treatment-received-analysis

Question 21

number of people who need to receive a new treatment to prevent one adverse event from occurring

Answer 21

number-needed-to-treat (NNT)

Question 22

frequency of the outcome in the control (current best practice treatment or placebo) group

Answer 22

control event rate (CER)

Question 23

frequency of the outcome in the experimental (new treatment) group

Answer 23

experimental event rate (EER)

Question 24

the reduction in risk (probability of the outcome) that is conferred by the new treatment

Answer 24

absolute risk reduction (ARR)

Question 25

the outcome measurement in a study - the variable of interest such as the primary illness or disease status indicator

Answer 25

outcome variable

Question 26

characteristic that is hypothesized to influence the outcome variable - in clinical studies this is often the group to which patients have been randomized. In cross sectional and cohort studies these are often exposure variables

Answer 26

explanatory variables

Question 27

stats used when the outcome measurement has a distribution that is approximately normal

Answer 27

parametric statistics

Question 28

squared term that describes the total variation in the sample

Answer 28

variance

Question 29

meausre of variability that describes how far the data spreads on either side of the central mean value. It is the square root of the variance and therefore is in the same units as the data values

Answer 29

standard deviation (SD)

Question 30

data points at the extremities of the range or separated from the normal range of data values. Data points are MORE THAN 3 SD from the mean are usually considered this

Answer 30

outlier

Question 31

calculated by dividing a mean value by its SE - gives a number from which the probability of the event occurring is estimated from a t-distribution

Answer 31

T-value

Question 32

this is closely related to a normal distribution but depends on the number of cases in the sample

Answer 32

T-distribution

Question 33

test to measure whether a continuous outcome variable with a normal distribution is significantly different between two groups - example between male or female or between an intervention and a control group

Answer 33

independent samples T-test

Question 34

test used to compare the mean values of two independent samples using a normal distribution - only used when the sample size is very large or the mean and SD of the population are known

Answer 34

unpaired Z-test

Question 35

distance between two mean values, described in units of their SD that describes the relative magniftute of the difference between two groups

Answer 35

Effect size

Question 36

Pearson's correlation coefficient that measures the strength of a linear relationship between two continuous normally distributed variables

Answer 36

R value

Question 37

coefficient of determination is equal to the squared correlation coefficient and provides an estimate of the percent of variation in one variable that is explained by the other variable

Answer 37

R ^2

Question 38

sample taken from a population in which all people have an equal chance of being selected

Answer 38

random selection

Question 39

range of values in which the majority of people in a population expected to lie

Answer 39

normal values

Question 40

distance between an observed value and its predicted value - in this case the value predicted by the regression line

Answer 40

residuals

Question 41

regression line through a set of data points calculated to minimie the sums of squared residuals

Answer 41

line of best fit

Question 42

study which is conducted to measure rates of disease in a population or to meausre associations between exposures (risk factors) and disease

Answer 42

observational study

Question 43

study conducted to test the effect of a treatment or intervention

Answer 43

experimental study

Question 44

study which is conducted to measure whether a new treatment is superior or equivalent to no treatment or an existing treatment - participants are randomly allocated to the study groups

Answer 44

randomized controlled trial

Question 45

study in which participants receive two or more treatments given consecutively usually in random order. The response to the first treatment can be contrasted with the response to the second treatment in the same participants

Answer 45

cross-over trial

Question 46

test to measure whether the means of two related continuous meausres are different from one another, typically measurements taken from the same participants on 2 occasions

Answer 46

Paired T-test

Question 47

outcome of interest which is typically death but can be non-fatal or favorable outcome such as discharge from hospital

Answer 47

event

Question 48

used to describe participants who withdraw from the study or who do not experience the outcome of interest

Answer 48

censored observations

Question 49

statistic used to compare the event rate over time between two or more study groups - also called long-rank test

Answer 49

Kaplan-Meier statistic

Question 50

risk of the event in a study group divided by the risk of the event in a reference group

Answer 50

Hazard ratio

Question 51

test used to confirm a disease in people who present with signs or symptoms

Answer 51

diagnostic test

Question 52

test regarded as the most accurate method available for classifying people as disease positive or negative

Answer 52

gold standard

Question 53

probability of a positive test in a person with the disease compared to the probaility of a positive test in a person without disease

Answer 53

likelihood ratio

Question 54

proportion of test-negative people who do not have the disease

Answer 54

negative predictive value

Question 55

proportion of test-positive people who have the disease

Answer 55

positive predictive value

Question 56

test used for early identification of disease in a population without symptoms

Answer 56

screening test

Question 57

proportion of disease positive people who are test-positive

Answer 57

sensitivity

Question 58

proportion of disease-negative people who are test-negative

Answer 58

specificity

Question 59

meausre of precision with which the mena value has been measured

Answer 59

Standard Error (SE)