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Pulmonary Review > Epidemiology and Statistics > Flashcards

Epidemiology and Statistics Flashcards

1
Q

This is the study of illness outcomes by observing and comparing events in a group of individuals with shared characteristics.

A

Clinical epidemiology

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2
Q

What are 2 measures of disease occurrence?

A

Incidence and prevalence

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3
Q

What are 2 measures of disease outcomes?

A

Mortality and morbidity

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4
Q

What are some measures of validity or performance of diagnostic and screening tests?

A

Sensivity
Specificity
Predictive values
Likelihood ratios

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5
Q

What are some measures of disease association?

A 
Odds ratio (OR)
Relative Risk (RR)
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6
Q

Define odds ratio

A

(odds of disease in population A)/(odds of disease in population B)

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7
Q

This measure can give you mortality of a certain disease, usually calculates as a/(a+b)

A

Proportion

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8
Q

This is the equation where (a = frequency of events during a certain time period)/(a+b)

A

Rate

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9
Q

Is prevalence a proportion or a rate?

A

Proportion

Incidence is a rate!

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10
Q

This is the (new cases)/(subjects x yrs of follow-up per subject)

A

Incidence rate

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11
Q

What is the prevalence rate?

A

PR = (# individuals with disease)/(total population at a specific time)

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12
Q

In a population of 1000 people in which 50 are sick with H1NI flu illness and 25 die from H1NI in 1 year, what is the mortality rate?

A

Mortality rate from H1NI in that year = 25/1000

= 0.025 or 2.5%; case rate for H1NI disease = 25/50 = 0.5 or 50%

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13
Q

In a table of disease and testing, what is:

a/a+c

A

Sensitivity

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14
Q

In a table of disease and testing, what is:

d/b+d

A

Specificity

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15
Q

What one (sensitivity or specificity) is use to rule in a disease?

A

Specificity

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16
Q

In a table of disease and testing, what is:

a/a+b

A

PPV

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17
Q

In a table of disease and testing, what is:

d/c+d

A

NPV

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18
Q

What will happen to PPV if there is low disease prevalence?

A

Decrease

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19
Q

What will happen to NPV if there is low disease prevalence?

A

Increase

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20
Q

This is the true positive/false positive

aka sensitivity/(1-specificity)

A

+LR

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21
Q

What is the equation for negative likelihood ratio?

A

false negative/true negative

aka

1-sensitivity/specificity

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22
Q

This is the ability of a test to detect which individuals have the disease and which do not have the disease

A

Validity

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23
Q

This is the consistency of results under repeated measurements by the same individuals under the same conditions

A

Reliability/repeatability

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24
Q

This is the number of individuals needed to be screened for a given duration to prevent or detect one outcome

A

Number needed to screen

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25
Q

This is the bias that reflects the observed lengthening of survival time due to earlier diagnosis by a screening test without any actual prolongation of survival

A

Lead time bias

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26
Q

This is the bias that reflects the increased likelihood of identification of indolent tumors by intermittent screening as compared to fast growing/aggressive tumors that can be missed due to their rapid progression

A

Length-time bias

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27
Q

This is the bias that reflects the identification of disease by a screening test that does not affect the patients life in the absence of screening (aka pseudodisease aka benign lung nodules)

A

Overdiagnosis bias

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28
Q

This is the application of statistical tools and methods to address and analyze problems in health and medicine

A

Biostatistics

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29
Q

This type of study has the following advantages/disadvantages:

Advantages- quick and inexpensive, feasible for rare disorders, fewer subjects needed thank cross-sectional studies, generates OR

Disadvantages- reliance on recall or records to determine exposure, selection bias, selection of control groups is difficult

A

Case-control studies

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30
Q

This type of study has the following advantages/disadvantages:

Advantages- ethically safe, easier and cheaper than RCT, matching is possible, can establish timing and directionality, eligibility criteria and outcome can be standardized, generates RR

Disadvantages- difficult to identify controls, blinding is difficult, randomization not present, needs large sample sizes, expensive to conduct

A

Cohort study

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31
Q

This type of study has the following advantages/disadvantages:

Advantages- quick, cheap, simple, and ethically safe, population-based, best for quantifying the prevalence of a disease or risk factor

Disadvantages- establishes association and not causality, recall bias, confounders may be distributed

A

Cross-sectional study

32
Q

This type of study has the following advantages/disadvantages:

Advantages- unbiased distribution of confounders, blinded, no bias, follow-up usually complete

Disadvantages-expensive volunteer bias, ethically problematic, loss of follow-up

A

RCT

33
Q

This type of RCT randomizes entire groups rather than individual subjects to treatment

Ex: A hospital randomizes antibiotic cycling and measures infection rates

A

Cluster RCT

34
Q

This type of RCT randomizes 2 or more treatments/interventions in all possible combinations

Ex: effect of salmeterol + fluticasone vs tiotropium _ salmeterol + fluticasone vs salmeterol alone in COPD exacerbations

A

Factorial randomized design

35
Q

This type of RCT randomly allocates each patient to a sequence that includes each treatment so that each patient can act as their own control for treatment

A

Crossover design

36
Q

This is an evidence-based resource produced after reviewing published and unpublished studies and combining the information of all relevant studies to address a particular clinical question.

A

Systematic review

37
Q

This is a type of systematic review that uses systematic methods to combine qualitative and quantitative study data from several selected studies

A

Meta analysis

38
Q

Put the following study designs in the heirarchy of form of evidence from lowest to highest:

Case report
Observational cohort
Case-control
Meta analysis
RCT
Expert opinion
Case series
A 
Lowest: expert opinion
Case report
Case series
Case-control
Observational cohort
RCT
Highest: Meta-analysis
39
Q

This is the sum of all observations divided by count of total number of observations, used for continuous variables, and easily distorted in a skewed data set

A

Mean

40
Q

When is it beneficial to use the median in data sets?

A

When distribution is not normal, as it’s not affected by extreme values

41
Q

This is the most frequent observation in the data set, used for discrete variable

A

Mode

42
Q

This is (a/a+b)/(c/c+d)

A

RR

basically (risk in exposed)/(risk in non-exposed)

43
Q

What does it mean if the RR=1?

A

No association

44
Q

What does it mean when the RR >1?

A

Positive association - risk in exposed is greater than nonexposed

Ex: smokers are at high risk for developing lung cancer

45
Q

What does it mean when the RR<1?

A

Exposed is less than that in nonexposed

Ex: daily exercise protects against heart disease

46
Q

This is the ratio of odds of disease in the exposed group to the odds of diseaase in the non-exposed group

A

OR

47
Q

TRUE/FALSE: OR is used in both cohort and case-control studies

A

TRUE

48
Q

Give me the following letter (abcd) ratios to define the following OR calculations:

Odds of disease in exposed
Odds of disease in nonexposed
OR of disease in exposed
OR of exposure in diseased

A

Odds of disease in exposed = a/b

Odds of disease in nonexposed = c/d

OR of disease in exposed = ad/bc

OR of exposure in diseased = ad/cb

49
Q

What does it mean when the OR=1?

A

No association of exposure with disease or disease with exposure

50
Q

What does it mean when the OR>1?

A

Exposure or disease is positively related

Ex: odds or getting lung cancer is higher in smokers or odds of smoking exposure is higher in lung cancer patients

51
Q

What does it mean when the OR<1?

A

Exposure or disease is negatively related

Ex: odds of developing heart disease is lowers in individuals who perform daily exercise (protective)

52
Q

This test is used to measure statistical difference and is used to compare the MEANS from 2 different samples in a NORMALLY distributed data set

A

t-test

53
Q

This test is used to determine if there are significant differences between variances of multiple samples

A

ANOVA

54
Q

This test is used to determine the association between 2 categoric variables from 2 or more independent groups in the form of a 2x2 table

Compares the frequency distribution from observed data to the frequency distribution that would be expected under null hypothesis of no association

A

Chi-squared test

55
Q

This analysis is used to estimate the influence of one or more independent variables and predict the value of the dependent variable, allows good control of confounders

A

Regression analysis

56
Q

Which is used for a continuous dependent variable: logistic or linear regression?

A

Linear regression

57
Q

This is a statement of no effect or no association.

A

Null hypothesis

58
Q

This is the probability that the results observed in a study may have been just a chance finding.

A

P-value (statistical significance)

59
Q

TRUE/FALSE: p-values indicate the strength and/or direction of the association

A

FALSE

They depend heavily on the sample size
and effect size

60
Q

This is the range within the true value of a parameter lieis

A

Confidence interval (CI)

61
Q

What does a 95% CI mean?

A

A 95% CI indicates 95% certainty that the interval contains the true value of the expected outcome in the entire population

62
Q

True/False: Precision of CI depends on the sample size and variation

A

TRUE

larger sample sizes and less variation have norrower CIs, meaning more precision in results and vice versa

63
Q

This error is a rejection of the null hypothesis when the null hypothesis is true (false+)

A

Type I error

64
Q

What is a type II error?

A

Accepting the null hypothesis when it’s false (false-)

65
Q

This is the probability of finding a true differnece when the difference really exists or the probability of correctly rejecting the null hypothesis when it’s false

A

Power

Ex; if the probability of a type II error is 5%, the statistical power is 95%

66
Q

What’s considered a good power level?

A

> 9000

or in research, 80-90% power

67
Q

What is selection bias?

A

Errors in participant selection or bias in the assignment of participants

68
Q

What is information bias?

A

Errors in data collection and poor categorization in exposure or otucome status

69
Q

What is recall bias?

A

Poor recall or memory of exposure status in case-control studies

70
Q

What is interviewer bias?

A

Results obtained differnetly in the disease vs control groups by unblinded interviewers

71
Q

What is publication bias?

A

Preferential publication of striking result in small studies

AKA every COVID paper thus far.

72
Q

This is a variable that can cause or prevent the outcome of interest independently and is not an intermediate variable

A

Confounder

73
Q

What is essential for external validity (aka generalizability)?

A

Internal validity

74
Q

Why do we care about intention to treat analysis?

A

Measures effectiveness (aka real world care) rahter than efficacy

75
Q 
241 of 487 patients treated
with salmeterol (49.5%)
and 210 of 507 patients
treated with
salmeterol/fluticasone
(41.4%) had at least one
exacerbation over the 44-
week trial. What is the NNT
to prevent one
exacerbation for
salmeterol/fluticasone
group?
A 
The absolute risk reduction
(ARR) of 49.5%–41.4% =
8.1%. NNT with
salmeterol/fluticasone
(rather than salmeterol
alone) to prevent one
additional patient from
experiencing an
exacerbation in 44 weeks =
1/0.081 = 12.3.

Pulmonary Review (14 decks)

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