Question

7. The following table cross-classifies pregnant women in the study by their body mass index (BMI) at 16 weeks gestation and whether they had pre-term delivery. What proportion of women with BMI greater than 35 delivers pre-term?

BMI < 30

BMI 30–34.9

BMI 35+

Pre-term

320

80

120

Full term

4700

480

300

A)0.0867

B)0.2857

C)0.0533

D)0.533

Answer 1

Solution

The given data is reproduced in a 3 x 2 contingency table below along-with the marginal (row and column) totals and grand total:

BMI	Delivery Term		Total
	Pre-term	Full-term
< 30	320	4700	5020
30 – 34.9	80	480	560
35 +	120	300	420
Total	520	5480	6000

Out of 420 women with BMI 35 +, 120 had pre-term delivery. Therefore,

proportion of women with BMI greater than 35 delivering pre-term =120/420 = 0.2857.

Thus, Option B Answer

DONE