A doctor wants to research if there is any difference in birth weights of a mother's first and second children. To do this, he randomly selects 10 mothers with two children. Calculate the test...

A doctor wants to research if there is any difference in birth weights of a mother's first and second children. To do this, he randomly selects 10 mothers with two children. Calculate the test statistic and degrees of freedom for an appropriate hypothesis test using the data set below. Let the difference d for each case be computed as d=second−first. Assume that the weights are normally distributed. Round the test statistic to three decimal places.

First (lbs) Second (lbs)
6.2              5.9
7.5              6.9
8                 8.8
7.4               7
9.1              8.1
7.1              7.7
6.3              6.3
7                 6.1
6.9              7.1
8.9              8.4