Question

A public relations firm found that only 27% of voters in a certain state are satisfied with their U.S. senators. How large a sample of voters should be drawn so that the sample proportion of voters who are satisfied with their senators is approximately normally distributed?a) 38b) 14c) 10d) 48

Answer 1

a) 38

Explanation:

The normal distribution can be applied if:

`np \geq 5` and
`n(1-p) \geq 5`

In this question:

`p = 0.27`

Then

a) 38

n = 38.

Then

38*0.27 = 10.26

38*0.73 = 27.74

Satisfies. But is this the smallest sample of the options which satisfies.

b) 14

n = 14

Then

14*0.23 = 3.22

14*0.77 = 10.78

Does not satisfy

c) 10

Smaller than 14, which also does not satisfy, so 10 does not satisfy.

d) 48

Greater than 38, which already satisfies. So the answer is a)