A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies. Random samples of 5 babies' weights (pounds) for each gender showed the following: $$\begin{array} { l l l l l l }
\text { Boys } & 8.0 & 4.7 & 7.3 & 6.2 & 3.4 \
\text { Girls } & 5.3 & 2.8 & 6.4 & 6.8 & 7.4
\end{array}$$ To test the researcher's hypothesis, we should use the:
A)paired (dependent) samples t-test.
B)independent samples t-test.
C)large-sample z-test.
D)t-test for correlation.

Question

A medical researcher wondered if there is a significant difference between the mean birth weight of boy and girl babies. Random samples of 5 babies' weights (pounds) for each gender showed the following: $$\begin{array} { l l l l l l } 
\text { Boys } & 8.0 & 4.7 & 7.3 & 6.2 & 3.4 \
\text { Girls } & 5.3 & 2.8 & 6.4 & 6.8 & 7.4
\end{array}$$ To test the researcher's hypothesis, we should use the:
A)paired (dependent) samples t-test.
B)independent samples t-test.
C)large-sample z-test.
D)t-test for correlation.

Quizplus · Accepted Answer

We should use an independent samples t-test because the samples (boys and girls) are independent of each other. We are testing for a difference in means between two groups, and the sample size is too small for a large-sample z-test. A paired samples t-test would be used if we were comparing the same group of babies before and after a treatment, and a t-test for correlation would be used if we were testing for a relationship between two variables.