# Need help with a question for homework

#### sherichance

##### New Member
Stratification
Oral Contraceptive (OC) use is hypothesized to increase the risk of stroke. Assume that oral contraceptive use is inversely associated with age (younger women are more likely to use OCs compared to older women), and that age is positively associated with stroke (older women are more likely to have a stroke compared to younger women).
• Is age associated with the exposure? The outcome? Is it in the causal pathway of interest? (1 point)
• Calculate the crude OR (2points)
Stroke No Stroke Total

OC Use 86 683 769
No OC Use 93 959 1052
Total 179 1642 1821

• Ages 20-39
Ages 40-49
Ages 50-54

Stroke
No stroke
Stroke
No stroke
Stroke
No stroke
OC Use
13
51
31
301
42
331
No OC Use
46
285
30
463
17
211
Total
59
336
61
764
59
542
Stratify by the potential confounder, calculate stratum-specific ORs Stratified by age
Odds ratio (age 20-39)
Odds ratio (age 40-49)
Odds ratio (age 50-54)
Summary (age-adjusted) odds ratio* = 1.57
* The summary OR was calculated using a statistical procedure known as the Mantel-Haenszel weighted odds ratio. You will learn about this measure in future epidemiology and biostatistics classes. (6 points)
• As the investigator, which measure of effect (crude or adjusted) would you choose to report to your audience? (2 points)

#### Karabiner

##### TS Contributor
So, which answers would you suggest?

With kind regards

Karabiner