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Biostats > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

What makes a fair comparison?

A

Randomized participants

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2
Q

Observations

A

Group of people/what surveying

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3
Q

Variables

A

What’s being measure

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4
Q

Categorical

A

small number of values

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5
Q

Binary

A

2 possible values (yes or no)

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6
Q

Nominal

A

order of categories is irrelevant

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7
Q

Ordinal

A

order of categories is meaningful

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8
Q

Discrete

A

values equal to integers

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9
Q

Continuous

A

values on a continuum

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10
Q

Histogram

A

graphical display of the distribution of quantitative data

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11
Q

In a stem and leaf plot, which digits are the stem and which are the leaf?

A

Stem is 1st digits and leaf is last digit

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12
Q

Central tendency

A

the middle of the data

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13
Q

Variation

A

how “spread out” the data is

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14
Q

Mean

A

average of all values in dataset

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15
Q

Median

A

middle value

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16
Q

Mode

A

most common value

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17
Q

mean > median

A

right (positively) skewed

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18
Q

mean < median

A

left (negatively) skewed

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19
Q

mean = median

A

symmetrical

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20
Q

Range

A

smallest and largest values in data

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21
Q

Interquartile Range (IQR)

A

25th and 75th percentile (1st and 3rd quartiles)

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22
Q

Varience

A

average of (X-X bar)^2

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23
Q

Standard deviation

A

square root of varience

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24
Q

What is the box of a box and whisker plot?

A

25th to 75th percentile

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25
Q

Scatter plot

A

Illustrates the relationship between 2 quantitative measures

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26
Q

Correlation

A

a numerical descriptive of the strength of a linear association between 2 variables

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27
Q

r > 0

A

higher values of one variable correspond to higher values of the other

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28
Q

r < 0

A

higher values of one variable correspond to lower values of the other

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29
Q

r = +/-1

A

perfect linear association

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30
Q

r = 0

A

no linear association

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31
Q

Cumulative incidence

A

proportion of individuals newly acquiring the disease over a specific period of time

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32
Q

Risk factor

A

variable that may increase or decrease the chance (risk) of outcome

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33
Q

Relative risk

A

a measure of the strength of an association

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34
Q

RR < 1

A

treatment is associated with lower risk of outcome

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35
Q

RR > 1

A

treatment is associated with higher risk of outcome

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36
Q

RR = 0

A

no association of treatment with outcome

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37
Q

How do you calculate relative risk?

A

risk (treated) / risk (untreated)

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38
Q

Risk difference

A

how much of the disease can be attributed to a risk factor

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39
Q

How do we calculate risk difference?

A

risk (treated) - risk (untreated)

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40
Q

RD < 0

A

treatment associated with lower risk of outcome

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41
Q

RD > 0

A

treatment associated with higher risk of outcome

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42
Q

RD = 0

A

no association of treatment with outcome

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43
Q

What is the wording when reporting risk difference?

A

percentage point increase/decrease

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44
Q

What is the wording when reporting relative risk?

A

Percent increase/decrease

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45
Q

What constitutes stronger association when comparing risk difference?

A

A value farther away from 0

46
Q

Incidence Rate (IR)

A

number of people who develop a condition (incident events) per person in the population over time

47
Q

What are the units for incidence rate?

A

per person-years

48
Q

Censored

A

when participants drop out or have not had the event by the end of follow-up

49
Q

Cumulative Incidence

A

similar to incidence rate but for a specific length of time. can’t calculate if there are drop outs

50
Q

Incidence Rate Ratio (IRR)

A

IR (treated) / IR (untreated)

51
Q

IRR < 1

A

treatment associated with lower rate of outcome (protection)

52
Q

IRR > 1

A

treatment associated with higher rate of outcome (harmful)

53
Q

IRR = 1

A

No association between treatment and outcome

54
Q

Incidence Rate Difference (IRD)

A

IR (treated) - IR (untreated)

55
Q

IRD < 0

A

treatment associated with lower rate of outcome (protection)

56
Q

IRD > 0

A

treatment associated with higher rate of outcome (harmful)

57
Q

IRD = 0

A

No association between treatment and outcome

58
Q

Prevalence

A

the fraction of individuals with the disease at one specific point in time

59
Q

PR < 1

A

exposure associated with lower prevalence

60
Q

PR > 1

A

exposure associated with higher prevalence

61
Q

PR = 1

A

no association between exposure and outcome

62
Q

Prevalence Ratio

A

PR

63
Q

Prevalence Difference

A

PD

64
Q

PD < 0

A

exposure associated with lower prevalence

65
Q

PD > 0

A

exposure associated with higher prevalence

66
Q

PD = 0

A

no association between exposure and outcome

67
Q

Population

A

collection of all individuals (units) that you wish to make inferences about

68
Q

Parameter

A

numerical value that would be calculated using all units in the population

69
Q

Sample

A

subset of “units”

70
Q

Estimate/statistic

A

numerical value that is calculated using all units in the sample

71
Q

Sampling unit

A

the individual items or elements of the population that are to be sampled (individual people, census tracts, houses)

72
Q

Sampling Frame

A

a list of all units in the population (census tracts, class list, entire households)

73
Q

Probability sampling

A

each unit in the population has a known, non-zero chance of being selected from the population to be included in the sample

74
Q

Simple random sample

A

randomly selected individuals from the population such that each individual has the same change of being selected

75
Q

Stratified random sample

A

divide population into subgroups and take simple random sample from each subgroup

76
Q

Systematic random sample

A

randomly choose a starting unit; sample ___th unit after the starting unit

77
Q

Cluster sample

A

sample clusters of individuals (households, clinics, schools) and use all individuals in the cluster

78
Q

Multistage random sample

A

sample in stages (1st = school, 2nd = classroom, 3rd = student)

79
Q

Convenience Sample

A

samples that aren’t selected probabilistically

80
Q

Generalizability

A

a measure of how useful the results of a study are for a broader group of people or situations

81
Q

When is a sampling method bias?

A

if it produces results that systematically differ from the population

82
Q

When is a sampling method unbias?

A

if over repeated sample, the average of the estimates from those sample can be expected to equal the parameter in population of interest

83
Q

Selection bias

A

the sampling procedure systematically includes or excludes a portion of the population

84
Q

Social desirability or response bias

A

subjects may not answer truthfully

85
Q

Hawthorne effect

A

alteration of behavior by the subjects of a study due to their awareness of being observed

86
Q

Low variability / high precision (bull’s eye)

A

estimates tightly cluster around each other

87
Q

Unbiased (bull’s eye)

A

estimates cluster around the bull’s eye

88
Q

Margin of error (MOE)

A

measure of the precision of an estimate and gives a plausible range of values for the parameter

89
Q

What provide a higher level of evidence, experimental or observational studies?

A

Experimental

90
Q

Experimental Study

A

Exposure or treatment is controlled by the researcher

91
Q

Replication

A

Same treatments are assigned to different sampling units to help assess variation in the responses

92
Q

Randomization

A

ensure that uncontrolled factors do not bias the experimental results

93
Q

Observational Study

A

exposure or treatment is not controlled by the researcher. Researchers collect data from an existing situation

94
Q

Confounder

A

a variable that changes the estimate of the association between the main independent variable of interest (exposure) and the dependent variable (outcome) by 10% or more

95
Q

Mediator

A

variable in the causal pathway that is associated with exposure and outcome

96
Q

Case Reports

A

Describe characteristics of a few individual patients

97
Q

Ecological Study

A

a study of risk-modifying factors and health or other outcomes based on populations defined either geographically or temporally

98
Q

Cross-sectional Study

A

Samples populations and measures diseased/not diseased and exposed/not exposed at the same time

99
Q

Case-control Study

A

Samples diseased and not diseased individuals separately and then measures exposed/not exposed

100
Q

Odds Ratio

A

odds of exposed among those with disease/odds of exposure among those w/o disease

101
Q

OR of exposure comparing diseased to not diseased =

A

OR of disease comparing exposed to unexposed

102
Q

Relative risk and odds ratio will always estimate the same direction of association

A

OR < 1 if and only if RR < 1
OR > 1 if and only if RR > 1
OR = 1 if and only if RR = 1

103
Q

Odds ration is always at least as extreme as the relative risk

A

If RR < 1, then OR </= RR < 1
If RR > 1, then OR >/= RR > 1

104
Q

When the risk of disease is relatively low, the OR and RR are similar

A

RR = OR

105
Q

Cohort Study

A

Enroll healthy participants and follow over time to see who develops disease

106
Q

Randomized Clinical Trial

A

Study population —> randomize —> split into intervention and control —> measure outcome

107
Q

Meta-analysis

A

a way of combining results from multiple existing studies

108
Q

Pre-clinical work

A

testing of a drug in-vitro and in animals to get a sense of toxicity, metabolism, PK, dosing

109
Q

Phase 1 CT

A

drug given to usually healthy volunteers to determine safety and appropriate dosing levels. no controls

110
Q

Phase 2 CT

A

further explore safety and get an initial idea of efficacy. control group usually used

111
Q

Phase 3 CT

A

large, definitive RCT designed to show safety and efficacy. usually double blind, placebo controlled

Biostats (2 decks)

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