We are told that the data is representative of the two populations (U.S. males aged 20-29 years and U.S. males aged 75+ years), and we will assume that researchers collected random samples. The samples are very large; therefore, the conditions are met for use of the T-test.

Using StatCrunch, we find a T-score of 5.3 and a P-value of "< 0.0001."

What can we conclude?

A) The data prove that, in the U.S., young men weigh about 4.9 kgs more on average than old men.

B) The data suggest that young men weigh more on average than old men in the U.S., but that the difference in mean weights for the two groups is not statistically significant.

Notice:- B) Not quite right. It is true that the data support the alternative hypothesis, but the differences are statistically significant since the P-value is essentially zero.

C) The data provide strong evidence that young men weigh more on average than old men in the U.S.

D) no conclusion is possible because we did not specify a significance level