Chapter 13, Problem 32E

a)

To determine

To explain the importance of randomization.

Answer to Problem 32E

Randomization is important to equalize two groups.

Explanation of Solution

There might be bias in the results or in the subjects. Therefore, to reduce this bias and equalize groups with respect to unknown factor we need randomization. Self-selection might create a bias in the results.

b)

To determine

To explain why the meals prepared by dieticians.

Explanation of Solution

The reason behind the food prepared by dieticians is that we are sure that the subjects will not deviate from the diet. That helps to all subjects will eat comparable food and followed all diet plans.

c)

To determine

To explain the use of control group.

Explanation of Solution

The control group is used to sure about the variations happened by chance. Therefore, the researchers can compare the change in blood pressure observed in the DASH group to the control group. This helps to identify whether the lurking variables would be the cause of the lower blood pressure.

d)

To determine

To explain whether the average is statistically significant.

Answer to Problem 32E

The average is statistically significant if the standard deviation is small.

Explanation of Solution

The variation is the blood pressure measured by standard deviation. If the standard deviation is small then 6.7 points would be significant change otherwise the average is not statistically significant.