Lectures 7-9 - Measures of Association

Question 1

What is an absolute difference?

Answer 1

The absolute value of the difference (subtraction) of frequencies.

Question 2

What is a relative difference?

Answer 2

The ratio (division) of frequencies.

Question 3

What is risk?

Answer 3

• probability of an outcome in an individual group
• proportion
• ex. A / (A + B)

Question 4

What is absolute risk reduction (ARR)?

Answer 4

The absolute value in the difference of risks.

• |risk in exposed - risk in unexposed|

Question 5

What is relative risk reduction (RRR)?

Answer 5

The quotient of the ARR and risk in unexposed.

-ARR / risk of unexposed

Question 6

What is number needed to treat/harm (NNT/H)?

Answer 6

The number of patients that need to be treated or exposed to receive the benefit or harm.

-1 / ARR

Question 7

What is a risk ratio?

Answer 7

The quotient of the risk of outcome in exposed and risk of outcome in unexposed.

• (A / (A + B)) / (C / (C + D))

Question 8

What factor must be presents in a comparison of ratios?

Answer 8

• the groups being compared
• direction of association (increased/decreased)
• magnitude

Question 9

What are odds?

Answer 9

Frequency of occurring vs. not occurring.

• ratio
• A / C or B / D

Question 10

What is an odds ratio?

Answer 10

• ratio of odds
• quotient of odds of exposure in diseased and odds of exposure in non-diseased
• (A x D) / (B x C)

Question 11

What is the name of the graph which visual represents ratio data?

Answer 11

Forest plot