Solution To Stat1600 Test #2 Form A Math Worksheet With Answers (Page 4 of 5) in pdf

Solution To Stat1600 Test #2 Form A Math Worksheet With Answers Page 4

From part (a), we can calculate the standard error of the estimated difference in pro-

portions:

.609

.609)

.045

.045)

SE =

.010353 + .001953 =

.012306 = .111

Hence the margin of error is M E = 1.96

.111 = .218. Consequently, we can get a

95% c.i. for p

(.564

.218, .564 + .218) = (0.346, 0.782)

which excludes 0. Therefore, the proportions differ and it appears that the heal rate

for the Treatment group is greater than that of the Placebo group.

Note that the interpretation of this 95% conﬁdence interval: we are 95% conﬁdent

that the difference in proportions (percentages) is in between 0.346 (34.6%) and and

0.782 (78.2%).

ulcers healed?

YES

Treatment

Placebo

Interpret your answer in words.

ANSWER (show your work):

The odds ratio is estimated as

odds

14/9

OR =

= 32.7.

odds

1/21

That is, the odds for those in the Treatment group to be healed is 32.7 times as high

as that for those in the Placebo group.

(d) (10 points) Estimate the ratio of proportions of those who were healed (YES) in the

two groups. Interpret your answer in words.

ANSWER (show your work):

Solution To Stat1600 Test #2 Form A Math Worksheet With Answers Page 4