Question

A researcher studying public opinion of proposed social security changes obtains a simple random sample of 50 adult Americans and asks them whether or not they support the proposed changes. To say that the distribution of the sample proportion of adults who respond yes, is approximately normal, how many more adult Americans does the researcher need to sample in the following cases? b. 25% of all adult Americans support the changes. b. The researcher must ask [] more American adults.

Answer 1

b) We have 25% support the changes, therefore solve:

$np(1-p)=10$

where p =25% = 0.25

So

$\begin{gathered} n(0.25)(1-0.25)=10 \\ n(0.25)(0.75)=10 \\ n(0.1875)=10 \\ \frac{n(0.1875)}{0.1875}=\frac{10}{0.1875} \\ n=53.3\approx54 \end{gathered}$

Need 54 people but already have 50, then:

$54-50=4$

Answer: 4