Question

Assume that we want to construct a confidence interval. Do one of the​ following, as​ appropriate: (a) find the critical value t Subscript alpha divided by 2​, ​(b) find the critical value z Subscript alpha divided by 2​, or​ (c) state that neither the normal distribution nor the t distribution applies. Here are summary statistics for randomly selected weights of newborn​ girls: n = 156​, x overbar = 33.3 ​hg, s = 7.9 hg. The confidence level is 95​%.

Select the correct choice below​ and, if​ necessary, fill in the answer box to complete your choice.

A. t Subscript alpha divided by 2equals nothing ​(Round to two decimal places as​ needed.)

B. z Subscript alpha divided by 2equals nothing ​(Round to two decimal places as​ needed.)

C. Neither the normal distribution nor the t distribution applies.

Answer 1

Solution :

Given that,

Point estimate = sample mean = = 33.3 hg

sample standard deviation = s = 7.9 hg

sample size = n = 156

Degrees of freedom = df = n - 1 = 156 - 1 = 155

correct option is = A

At 95% confidence level

= 1 - 95%

=1 - 0.95 =0.05

/2 = 0.025

t/2,df = t0.025,155 = 1.98