Final answer:
To calculate the point estimate for the mean value of strength, you should take the average of the differences data.
Step-by-step explanation:
To calculate the point estimate for the mean value of strength, you should take the average of the differences data. The differences data represents the change in weight lifted before and after completing the strength development class. So, calculate the mean by adding up the differences and dividing by the number of data points. In this case, the differences are {90, 11, -8, -8}, so the mean would be (90 + 11 + (-8) + (-8)) / 4 = 46.25.