A new sales training program has been instituted at a rent$-$to$-$own company. Prior to the training, six employees were tested on their knowledge of products offered by the company. Once the training was completed, the employees were tested again in an effort to determine whether the training program was effective. Scores are known to be normally distributed. The sample scores on the tests are listed next.

Pretest Score

Posttest Score

$66$

$75$

$94$

$100$

$87$

$93$

$84$

$85$

$76$

$75$

$88$

$90$

Use pre$-$test score as population $1$ and post$-$test score as population $2.$ Which of the following is the value of the appropriate test statistic?