Question

In? randomized, double-blind clinical trials of a new? vaccine, children were randomly divided into two groups. Subjects in group 1 received the new vaccine while subjects in group 2 received a control vaccine. After the first? dose, 118 of 746 subjects in the experimental group? (group 1) experienced fever as a side effect. After the first? dose, 51 of 623 of the subjects in the control group? (group 2) experienced fever as a side effect. Construct a 99?% confidence interval for the difference between the two population? proportions, p1-p2. Use x1=118?, n1=746?, x2=51?, and n2=623.

The 99?% confidence interval for p1-p2 is ?(____,_____)
?(Use ascending order. Round to three decimal places as? needed.)

Answer 1

The statistical software output for this problem is:

Two sample proportion summary confidence interval:
p₁ : proportion of successes for population 1
p₂ : proportion of successes for population 2
p₁ - p₂ : Difference in proportions

99% confidence interval results:

Difference	Count1	Total1	Count2	Total2	Sample Diff.	Std. Err.	L. Limit	U. Limit
p1 - p2	118	746	51	623	0.076314985	0.017295595	0.031764484	0.12086549

Hence,

99% confidence interval for p1 - p2 is:

(0.032, 0.121)