## A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 400 babies were born, and 340 of th

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 400 babies were born, and 340 of them were girls. Use the sample data to construct a 99% confidence interval estimate of the percentage of girls born. Based on the result, does the method appear to be effective? nothingless than pless than nothing (Round to three decimal places as needed.) Does the method appear to be effective? Yes, the proportion of girls is significantly different from 0.5. No, the proportion of girls is not significantly different from 0.5.

## Answers ( )

Answer:(a) 99% confidence interval for the percentage of girls born is [0.804 , 0.896].(b) Yes, the proportion of girls is significantly different from 0.50.Step-by-step explanation:We are given that a clinical trial tests a method designed to increase the probability of conceiving a girl.

In the study 400 babies were born, and 340 of them were girls.

(a) Firstly, the pivotal quantity for 99% confidence interval for the population proportion is given by;P.Q. = ~ N(0,1)

where, = sample proportion of girls born = = 0.85

n = sample of babies = 400

p = population percentage of girls born

Here for constructing 99% confidence interval we have used One-sample z proportion statistics.So, 99% confidence interval for the population proportion, p is ;P(-2.58 < N(0,1) < 2.58) = 0.99 {As the critical value of z at 0.5% level

of significance are -2.58 & 2.58}

P(-2.58 < < 2.58) = 0.99

P( < < ) = 0.99

P( < p < ) = 0.99

99% confidence interval for p= [ , ]= [ , ]

= [0.804 , 0.896]

Therefore, 99% confidence interval for the percentage of girls born is [0.804 , 0.896].(b)Let p = population proportion of girls born.So,

Null Hypothesis, : p = 0.50 {means that the proportion of girls is equal to 0.50}Alternate Hypothesis, : p 0.50 {means that the proportion of girls is significantly different from 0.50}The test statistics that will be used here is

One-sample z proportion test;statisticsT.S. = ~ N(0,1)

where, = sample proportion of girls born = = 0.85

n = sample of babies = 400

So,

=the test statistics= 19.604

Now, at 0.01 significance level, the z table gives critical value of 2.3263 for right tailed test.Since our test statistics is way more than the critical value of z as 19.604 > 2.3263, so we have sufficient evidence to reject our null hypothesis due to whichwe reject our null hypothesis.Therefore, we conclude that the proportion of girls is significantly different from 0.50.