Biostatics 4

Question 1

What study designs are commonly used in statistics?

Answer 1

Cross-sectional study, cohort study & randomized controlled trial (RCT), and case-control study.

Question 2

What does a cross-sectional study sample?

Answer 2

A subset of the study population.

Question 3

What measure of occurrence is used in cross-sectional studies?

Answer 3

Prevalence.

Question 4

What measure of association is used in cross-sectional studies?

Answer 4

Prevalence ratio.

Question 5

What samples are used in cohort studies and RCTs?

Answer 5

Sample of exposed and sample of unexposed.

Question 6

What measures of occurrence are used in cohort studies and RCTs?

Answer 6

Incidence proportion and incidence rate.

Question 7

What measures of association are used in cohort studies and RCTs?

Answer 7

Risk ratio and rate ratio.

Question 8

What samples are used in case-control studies?

Answer 8

Sample of cases and sample of non-cases.

Question 9

What measure of occurrence is used in case-control studies?

Answer 9

Odds

Question 10

What measure of association is used in case-control studies?

Answer 10

Odds ratio.

Question 11

What do we measure in a study involving smoking status and lung cancer status?

Answer 11

Smoking status (yes E+/no E-) and lung cancer status (yes D+/no D-).

Question 12

What would we measure in a cross-sectional study?

Answer 12

The prevalence of lung cancer in smokers and non-smokers.

Question 13

What measure of association would we report in a cross-sectional study?

Answer 13

Prevalence ratio.

Question 14

How would we interpret the prevalence ratio if it was 5.44?

Answer 14

Those who smoke were 5.44 times as likely to have lung cancer compared to non-smokers.

Question 15

What would we measure in a cohort study?

Answer 15

The incidence of lung cancer in smokers and non-smokers.

Question 16

What measure of association would we report in a cohort study using risk?

Answer 16

Risk ratio (relative risk).

Question 17

How would we interpret the risk ratio if it was 5.44?

Answer 17

Those who smoke had 5.44 times the risk of developing lung cancer compared to non-smokers.

Question 18

What is another measure of occurrence we could use in a cohort study?

Answer 18

Incidence rate.

Question 19

What measure of association would we report using the incidence rate?

Answer 19

Incidence rate ratio.

Question 20

How would we interpret the incidence rate ratio if it was 7.5?

Answer 20

Those who smoke had 7.5 times the rate of developing lung cancer compared to non-smokers.

Question 21

What important factors should we account for in a cohort study?

Answer 21

Loss to follow-up and death.

Question 22

When can you calculate odds instead of prevalence or incidence of disease?

Answer 22

When you cannot calculate prevalence or incidence of disease, you can calculate odds.

Question 23

How do you select participants in a case-control study?

Answer 23

You select participants as cases (with disease) and controls (without disease) and retrospectively assess exposure status.

Question 24

Why is the prevalence of cancer in a case-control study not meaningful?

Answer 24

Because the study design selects an equal number of cases and controls, making the prevalence artificially 50%.

Question 25

Can odds ratios (OR) be calculated in cohort or cross-sectional studies?

Answer 25

Yes, but they should not be interpreted as risk.

Question 26

How does the OR compare to the relative risk (RR)?

Answer 26

The OR always overestimates the RR.

Question 27

When does the OR approximate the RR?

Answer 27

The OR approximates the RR only when the disease is very rare (case-control study).

Question 28

Format of research protocol

Answer 28

Abstract
Introduction
Methods
Data management & analysis
Ethics
Resources
Logistics
References
Appendices