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NAPLEX > Chapter 14: Biostatistics > Flashcards

Chapter 14: Biostatistics Flashcards

1
Q

This kind of data has a logical order with values that continuously increase or decrease by the same amount (e.g., a HR of 120 BPM is twice as fast as a HR of 60 BPM)?

A

Continuous data

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2
Q

What is the difference between interval and ratio data?

A

Interval data has no meaningful zero (zero does not equal none) and ratio data has a meaningful zero (zero equals none)

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3
Q

What are the two types of discrete/categorical data?

A

Nominal and ordinal data

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4
Q

Which type of categorical data sorts subjects into arbitrary categories (names), such as male and female (0=male, 1=female or 0=female, 1=male)

A

Nominal data

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5
Q

Which type of categorical data is ranked and has a logical order, such as a pain scale?

A

Ordinal data

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6
Q

The mean is preferred for ____ data that is ____ distributed

A

Continuous; normally

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7
Q

The median is preferred for ____ data or ____ data that is skewed

A

Ordinal; continuous

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8
Q

The mode is preferred for ____ data

A

Nominal

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9
Q

Indicates how spread out the data is and to what degree the data is dispersed away from the mean

A

Standard deviation

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10
Q

Data that is highly dispersed has a ___ standard deviation

A

larger

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11
Q

Large sample sets of continuous data tend to form a ____ distribution

A

Gaussian or normal “bell-shaped”

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12
Q

When the distribution of data is normal, the curve is ____

A

Symmetrical (half of the values are on the left side and half of the values are on the right side)

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13
Q

When the distribution of data is normal, the mean, median and mode are ____ (the same or different)

A

The same

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14
Q

When the distribution of data is normal, __% of values fall within 1 SD of the mean and __% of the values fall within 2 SD of the mean

A

68%; 95%

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15
Q

Skewed distributions where 68% of the values do not fall within 1 SD of the mean and the mean, median and mode are not the same value usually occurs when the sample size is ___ and/or there are ____ in the data

A

Small; outliers

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16
Q

When there are a small number of values, an outlier has a ____ (small or large) impact on the mean and the data becomes skewed

A

Large

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17
Q

The distortion of the central tendency caused by outliers is ____ (increased or decreased) by collecting more values

A

Decreased

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18
Q

When there are more low values in a data set and the outliers are the high values, data is skewed to the ____ (left or right)

A

Right (positive skew)

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19
Q

When there are more high values in a data set and the outliers are the low values, data is skewed to the ____ (left or right)

A

Left (negative skew)

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20
Q

_____ states that there is no statistically significant difference between groups & is what the researcher hopes to disprove or reject

A

The null hypothesis

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21
Q

______ is what the researcher tries to prove or accept

A

The alternate hypothesis

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22
Q

When investigators design a study, they select a maximum permissible error margin, called ____, which is the threshold for rejecting the null hypothesis

A

Alpha

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23
Q

In medical research, alpha is usually set at ___

A

5% or 0.05

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24
Q

If the alpha is set at 0.05 and the p-value is less than alpha (p <0.05), is the null hypothesis rejected or accepted? Is the result termed statistically significant or insignificant

A

Rejected; statistically significant

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25
Q

A confidence interval provides the same information about significance as the p-value, plus the _____ of the result

A

precision

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26
Q

If alpha is 0.05, what would the confidence interval be?

If alpha is 0.01, what would the confidence interval be?

A

95%; 99%

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27
Q

When comparing means (difference data), when is a result statistically significant in regards to the confidence interval?

A

When the CI does not include zero
Example:
- The 95% CI for the difference in FEV1 between two drugs is 18-58 –> does not include zero, therefore the result is statistically significant
- The 95% CI for the difference in FEV1/FVC is -0.26-0.89 –> includes zero, therefore the result is not statistically significant

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28
Q

When comparing ratio data (relative risk, odds ratio, hazard ratio), the result is statistically significant if the CI range does not include ___

A

One

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29
Q

A narrow confidence interval range implies ____ (high or low) precision.

A wide confidence interval range implies ____ (high or low) precision.

A

High; low

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30
Q

Is a type I error a false-positive or false-negative?

A

False-positive

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31
Q

When alpha is 0.05 and a study result is reported with p <0.05, it is statistically significant and the probability of a type I error is ____

A

<5%

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32
Q

Is a type II error a false-positive or false-negative?

A

False-negative

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33
Q

Power is the probability that a test will ____ (accept or reject) the null hypothesis correctly

A

Reject

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34
Q

When is power used?

A

To avoid type II error

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35
Q

How can study power be increased?

A

Have a larger sample size

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36
Q

If beta is set at 0.2, what is the power?

A

80% - there is a 20% chance of missing a true difference and making a type II error

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37
Q

What is the relative risk formula?

A

RR = risk in treatment group/ risk in control group

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38
Q

What is the risk formula?

A

Risk = number of subjects in group with an unfavorable event/ total number of subjects in group

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39
Q

RR = 1 (or 100%) implies ___ (greater, lower, no difference) risk of the outcome between the groups

A

no difference

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40
Q

RR > 1 (or 100%) implies ___ (greater, lower, no difference) risk of the outcome in the treatment group

A

greater

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41
Q

RR < 1 (or 100%) implies ___ (greater, lower, no difference) risk of the outcome in the treatment group

A

lower

42
Q

What does relative risk reduction indicate?

A

How much the risk is reduced in the treatment group compared to the control group

43
Q

What is the relative risk reduction formula?

A

RRR = (% risk in control group - % risk in treatment group) / % risk in control group
-OR-
1-RR

44
Q

What is absolute risk reduction?

A

Includes the reduction in risk and the incidence rate of the outcome

45
Q

What is the formula for ARR?

A

ARR = (% risk in control group) - (% risk in treatment group)

46
Q

What is number needed to treat?

A

The number of patients who need to be treated for a certain period of time in order for one patient to benefit

47
Q

What is the NNT formula?

A

NNT = 1/ (risk in control group) - (risk in treatment group) OR 1/ARR

48
Q

What is number needed to harm?

A

Number of patients who need to be treated for a certain period of time in order for one patient to experience harm

49
Q

What is the formula for NNH?

A

NNH = 1/ARR (same formula as NNT)

50
Q

What is the difference between the NNH and NNT formula?

A

NNT is rounded up and NNH is rounded down

Example: NNT of 52.1 is rounded to 53, NNH of 41.9 is rounded to 41

51
Q

In order to estimate the risks associated with a treatment of some type of intervention in a CASE-CONTROL study, one should calculate ____

A

Odds ratio (or odds of unfavorable events)

52
Q

What kind of patients are enrolled in a case-control study?

A

Patients who have a clinical outcome or disease that has already occurred (e.g. lung cancer)

53
Q

In a case-control study, are medical charts reviewed prospectively or retrospectively?

A

Retrospectively

54
Q

What does odds-ratio tell us?

A

The odds of an outcome occurring with an exposure compared to the odds of the outcome occurring without the exposure

55
Q

What is the formula for odds ratio

A

OR = (# with outcome with exposure) x (# without outcome without exposure) / (# without outcome with exposure) x (# with outcome without exposure)

56
Q

What is a hazard rate?

A

Rate at which an unfavorable event occurs within a short period of time

57
Q

What is the hazard rate formula?

A

HR = hazard rate in treatment group/ hazard rate in control group

58
Q

How do you interpret an OR or HR = 1

A

The event rate is the same in the treatment and control arms. There is no advantage to the treatment

59
Q

How do you interpret an OR or HR > 1

A

The event rate in the treatment group is HIGHER than the event rate in the control group. For example, a HR of 2 for an outcome of death indicates that there are twice as many deaths in the treatment group

60
Q

How do you interpret an OR or HR < 1

A

The event rate in the treatment group is LOWER than the event rate in the control group. For example, a HR of 0.5 for an outcome of death indicates that there are half as many deaths in the treatment group

61
Q

What is a composite endpoint?

A

Combines multiple individual endpoints into one measurement

62
Q

T or F: All endpoints in a composite endpoint must be similar in magnitude and have similar, meaningful importance to the patient

A

True

63
Q

If continuous data is normally distributed, what test is appropriate to use to analyze the data?

A

Parametric methods

64
Q

If continuous data is NOT normally distributed, what test is appropriate to use to analyze the data?

A

Non-parametric methods

65
Q

Is a T-test a parametric or non-parametric method?

A

Parametric

66
Q

What is a one-sample t-test?

A

When data from a single sample group is compared with known data from the general population

67
Q

What is a paired t-test?

A

When a single-sample group is used for a pre- or post-measurement (i.e. the patient serves as their own control)

68
Q

When is a student t-test used?

A

When the study has TWO independent samples: the treatment and the control groups

69
Q

____ is used to test for statistical significance when using continuous data with 3 or more samples or groups

A

Analysis of variance (ANOVA) or F-test

70
Q

What type of test would you use for nominal or ordinal data (categorical data)?

A

Chi-square

71
Q

A statistical technique that is used to determine if one variable (such as number of days in hospital) changes or is related to another variable (such as incidence of hospital-acquired infection)

A

Correlation

72
Q

Describes the relationship between a dependent variable and one or more independent variables, or how much the value of the dependent variable changes when the independent variables changes.

A

Regression

73
Q

Which types of studies is regression common in?

A

Observational studies where researchers need to assess multiple independent variables or need to control for many confounding factors

74
Q

____ describes how effectively a test identifies patients WITH the condition

A

Sensitivity

75
Q

____ describes how effectively a test identifies patients WITHOUT the condition

A

Specificity

76
Q

A test with 100% sensitivity will be _____ (+ or -) in all patients with the condition

A

Positive

77
Q

A test with 100% specificity will be _____ (+ or -) in all patients without the condition

A

Negative

78
Q

A(n) _____ analysis includes data for all patients originally allocated to each treatment group (active and control) even if the patient did not complete the trial according to the study protocol

A

Intention-to-treat

79
Q

A(n) ____ analysis is conducted for the subset of the trial population who completed the study according to the protocol

A

Per protocol

80
Q

___ trials attempt to demonstrate that the new treatment has roughly the same effect as the old treatment

A

Equivalence

81
Q

___ trials attempt to demonstrate that the new treatment is no worse than the current standard based on the delta margin

A

Non-inferiority

82
Q

What type(s) of studies use forest plots?

A

Meta-analysis

83
Q

When interpreting statistical significance using a forest plot, what do the boxes represent?

A

Effect estimate. The size of the box correlates with the size of the effect from the single study shown

84
Q

When interpreting statistical significance using a forest plot, what do the diamonds represent?

A

Pooled results from multiple studies

85
Q

When interpreting statistical significance using a forest plot, what do the horizontal lines through the boxes represent?

A

The length of the CI for that particular endpoint (in a single study) or for the particular study (in a meta-analysis). The longer the line, the wider the interval, and the less reliable the study results. The width of the diamond in a meta-analysis serves the same purpose

86
Q

When interpreting statistical significance using a forest plot, what does the vertical solid line represent?

A

The line of no effect

87
Q

In a forest plot, what does it mean when data falls to the left of the solid line

A

A significant benefit has been reached

88
Q

In a forest plot, what does it mean when data falls to the right of the solid line

A

Significant harm

89
Q

The vertical line in a forest plot is set at __ for difference data and at __ for ratio data

A

0 ; 1

90
Q

This type of study compares cases (patients with a disease) to controls (patients without a disease)

A

Case-control

91
Q

This type of study compares patients with an exposure to those without an exposure

A

Cohort

92
Q

This type of study compares patients who were randomly assigned to groups

A

Randomized controlled trials

93
Q

This type of study analyzes the results of multiple studies

A

Meta-analysis

94
Q

Is a case-control study prospective or retrospective?

A

Retrospective

95
Q

Is a cohort study prospective or retrospective?

A

Prospective

96
Q

What is a limitation of a cohort study?

A

Can be influenced by confounders, which are other factors that affect the outcome (i.e. smoking, lipid levels)

97
Q

This type of study describes an adverse reaction or a unique condition that appears in a single patient

A

Case report

98
Q

This type of study describes an adverse reaction or a unique condition that appears in a few patients

A

Case series

99
Q

______ is used when 2 or more interventions have demonstrated equivalence in outcomes and the costs of each intervention are being compared

A

Cost-minimization analysis (CMAs)

100
Q

A systematic process used for calculating and comparing benefits and costs of an intervention in terms of monetary units (dollars)

A

Cost-benefit analysis (CBA)

101
Q

Used to compare the clinical effects of 2 or more interventions to the respective costs

A

Cost-effective analysis (CEA)

102
Q

A specialized form of CEA that includes a quality-of-life component of morbidity assessments, using common health indices such as quality-adjusted life years (QALYs) and disability-adjusted life years (DALYs)

A

Cost-utility analysis (CUA)

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