Biostatistics

Question 1

RRR

Relative Risk Reduction

Answer 1

1-RR

Question 2

RR

Relative Risk

Answer 2

Risk of Tx/Risk of Control

Question 3

A coffee creamer company recently learned that several lots ofproductwere contaminated with a human carcinogen. It is unknown what effect consuming this carcinogen in small quantities may have on humans. An immediate recall is announced. A massive media campaign is underway to identify people who used the lots of coffee creamer so they can receive medical attention immediately. The company plans to conduct a study to determine the effects of this exposure. They willfollowpeoplewho used the contaminated creamer over time and compare the rates of cancertopeople who used their coffee creamer, but who were not exposed to the contaminated lot. What study design does this trial represent?

A. Cross-sectional study

B. Case series

C. Case-control study

D. Cohort study

E. Case report

Answer 3

Cohort study

This is a prospective cohort study design.

Cohort studies start with an exposure/intervention and look for an outcome of interest (disease).

In this case the study starts with the exposure (contaminated coffee creamer) and patients will be followed prospectively to look for an outcome (disease such as cancer).

This design is useful when randomization to the exposure would be unethical.

Question 4

Case-Control Study

Answer 4

Compares pts w/ a disease (cases) to those w/out the disease (control)

Retrospective

Start w/ disease looks for exposure

Question 5

Cohort Study

Answer 5

Compares outcomes of a group of pts exposed & not exposed to a Tx

Prospective

Retrospective - less common

Start w/ exposure looks for disease

Question 6

Cross-sectional Survey

Answer 6

Estimates the relationship between variables & outcomes (prevalence) at one particular time (cross-section) in a defined population

Question 7

Case Report & Case Series

Answer 7

Describes an adverse rxn or a unique condition that appears in a single pt (case report) or a few pts (case series)

Outcome of the case is known

Case series is more reliable than a case report

Question 8

Randomized Controlled Trial (RCT)

Answer 8

Compares experimental Tx to a control (placebo or existing Tx)

Pts are randomized (have equal chance of being assigned to the Tx or control)

Sometimes blinded (unaware if they are receiving Tx or control)

Question 9

Randomized Controlled Trial (RCT)

Double-blind

Answer 9

Pt & investigator are unaware

Question 10

Randomized Controlled Trial (RCT)

Single-blind

Answer 10

Pt is unaware

Question 11

Randomized Controlled Trial (RCT)

Open label

or Unblinded

Answer 11

All parties know which Tx is being given to the pt

Question 12

Randomized Controlled Trial (RCT)

Parallel

Answer 12

Subjects are randomized to the Tx or control arm for the entire study

Question 13

Randomized Controlled Trial (RCT)

Crossover

Answer 13

Pts are randomized to 1 of 2 sequential Txs:
Group 1 - receive Tx A 1st, then crossover (change) to Tx B
Group 2 - receive Tx B 1st, then crossover (change) to Tx A

Question 14

Factorial Design

Answer 14

Randomizes to more than the usual 2 groups to test a number of experimental conditions

Question 15

Meta-analysis

Answer 15

Combines results from multiple studies in order to develop a conclusion that has greater statistical power than is possible from the individual smaller studies

Question 16

Systematic Review Article

Answer 16

Summary of the clinical literature that focuses on a specific topic or questions

Question 17

Types of Medical Studies

Least to Most Reliable

Answer 17

Expert Opinion

Case series & Case Report

Cast-Controlled Studies

Cohort Studies

Randomized Controlled Trials

Systematic Reviews & Meta-Analyses

Question 18

OR Formula

Answer 18

AD/BC

Question 19

Odds/Hazard Ratio

> 1

Answer 19

↑ in the likelihood

Question 20

Odds/Hazard Ratio

< 1

Answer 20

↓ in the likelihood

Question 21

Odds/Hazard Ratio

= 1

Answer 21

no correlation

Question 22

Odds Ratio

How to express OR > 1 in %?

Answer 22

OR x 100 - 100

Question 23

A pharmacist is considering which beta-blocker should be the preferred formulary agent at his institution. He has narrowed hisselection down to two agents. Each drug provides similar health benefits, has similar tolerability and is dosed once daily. The pharmacist will base his decision on the drug that can be purchased at the lower cost. This type of evaluation can be described as:

A. A cost-minimization analysis

B. A cost-effectiveness analysis

C. A cost-control analysis

D. A cost-benefit analysis

E. A cost-utility analysis

Answer 23

A cost-minimization analysis

If the benefit of two drugs or interventions is considered equivalent (e.g., there is no clinical benefit or harm of one compared to the other), a cost-minimization analysis can be used to determine which treatment is less expensive.

Question 24

The rate of the primary outcome was 1.28% per year in the apixaban groupand 1.60% per year in the warfarin group (95% CI, 0.66 to 0.95; p < 0.001 for noninferiority; p = 0.01 for superiority).

In this trial, the primary outcome is reported as a hazard rate (rate per year). Calculate the hazard ratio of the primary outcome in patients receiving apixaban compared to warfarin.(Express the answer as a decimal; no units or commas; round the final answer to the nearest TENTH.)

Answer 24

0.8

Hazard ratio (HR) = 1.28%/1.6% = 0.8. It is calculated in a similar way as risk ratio.

When HR < 1, this is favorable for the study drug as it means there were fewerunfavorable events in the treatment group.

Question 25

HR formula

Answer 25

Hazard rate Tx/Hazard rate Control

Question 26

Continuous Data

Answer 26

Data is provided by some type of measurement

Ratio & Interval

Question 27

Ratio Data

Answer 27

0 = None

Question 28

Interval Data

Answer 28

0 does not equal none

Question 29

Discrete Data

Answer 29

Categorical

Nominal & Ordinal

Question 30

Nominal Data

Answer 30

arbitrary order

Question 31

Ordinal Data

Answer 31

ranked in a logical order

Question 32

Student’s T-test

Answer 32

Continuous Data

2 independent groups

Question 33

Paired T-test

Answer 33

Continuous Data

2 paired groups

Question 34

ANOVA

Answer 34

Continuous Data

≥ 3 independent/paired groups

Question 35

Chi-Square

Answer 35

Nominal Data

≥ 2 independent groups

Question 36

McNemar

Answer 36

Nominal Data

2 paired groups

Question 37

Cochran’s Q

Answer 37

Nominal Data

≥ 3 paired groups

Question 38

Wilcoxon Rank Sum

Answer 38

Ordinal Data

2 independent groups

Question 39

Wilcoxon Signed Rank

Answer 39

Ordinal Data

2 paired groups

Question 40

Kruskal-Wallis

Answer 40

Ordinal Data

≥ 3 independent groups

Question 41

Friedman

Answer 41

Ordinal Data

≥ 3 paired groups

Question 42

Incremental Cost Rations Formula

Answer 42

(C2 - C1)/(E2 - E1)

Question 43

Cost-Minimization Analysis (CMA)

Answer 43

Compares cost of interventions w/ demonstrated equivalence

Question 44

Cost-Benefit Analysis (CBA)

Answer 44

Compares benefits & costs in monetary units

Question 45

Cost-Effectiveness Analysis (CEA)

Answer 45

Most common

Costs are monetary but outcomes are in clinical units (easty to quantify)

Question 46

Cost-Utility Analysis (CUA)

Answer 46

Outcomes based on quality-of-life assessments

Question 47

Intent to Treat

Answer 47

Data from ALL pts even the ones who did not complete the study

Question 48

Per Protocol

Answer 48

Data from ONLY the pts who completed the study

Question 49

The definition of sensitivity is best represented as:

A. The percentage of patients without a disease who have a negative test result.

B. The probability that an event will or will not occur.

C. The effect of an independent variable on a dependent variable.

D. The percentage of patients with a disease who have a positive test result.

E. The percentage of patients that will benefit from an intervention when a test result is positive.

Answer 49

The percentage of patients with a disease who have a positive test result.

Sensitivity is the percentage of “true-positive” results (a test is positive and the patient has the disease).

Question 50

Sensitivity

Answer 50

“True Positive”

Test is positive in patients w/ the condition

Question 51

Specificity

Answer 51

“True Negative”

Test is negative in patients w/out the condition

Question 52

A clinical trial is conducted on a new drug, LoSod. LoSod is found to reduce mean serum sodium to 131 mEq/L (95% confidence interval:128.7 mEq/L - 133.3 mEq/L). What is the correct interpretation of this study result?

A. There is a 95% chance that the confidence interval range contains the true population value for reduction in serum sodium with LoSod.

B. When using this drug in a larger population, 95% of patients will have a serum sodium between 128.7and 133.3 mEq/L.

C. When using this drug in a larger population, there is 95% confidence that the serum sodium will be reduced to 131 mEq/L.

D. There is a 5% chance that the true population mean is within the stated range.

E. There is more than a 5% chance that the results of the study are rejected in error.

Answer 52

There is a 95% chance that the confidence interval range contains the true population value for reduction in serum sodium with LoSod.

A confidence intervalis a range of values which is likely to includethe “true” population value.

It is more helpful than the p-value in estimating the effect of the outcome on the general population.

Question 53

Asmall, randomized, double-blind trial was conducted to evaluate a new treatment in patients with acute myocardial infarction. The primary endpoint, reduction in all-cause mortality, was not statistically significant.Which of the following is an accurate conclusion?

A. The inclusion and exclusion criteria were notdefined appropriately to reach statistical significance.

B. Further studies of the treatment should be discontinued immediately.

C. If there was any reduction in mortality, the treatment should be recommended for use.

D. A type I error may have occurred, preventing the ability to detect statistical significance.

E. The clinical trial may not have adequate statistical power.

Answer 53

The clinical trial may not have adequate statistical power.

Performing a larger trial will increase statistical power, which increases the probability that a type II error (not finding a difference when there is a difference) will be avoided.