Sherry collected the changes in 25-hydroxy vitamin D levels between before and after taking vitamin D supplements for a

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Sherry collected the changes in 25-hydroxy vitamin D levels
between before and after taking vitamin D supplements for a month
for 25 people with 25-hydroxy vitamin D deficiency. The data are
summarized below.

n=25; mean=5.0; standard deviation: 15

What's the two-sided p-value based on the test you select
in the previous question?
A. 0.055
B. 0.11
C. 0.01
D. 0.20
What's the smallest sample size that can make the
p-value in the previous test less than 5%?
A. 27
B. 39
C. 38
D. 26