random sample

Question

suppose the systolic blood pressure of a random sample of 100 students before exercising has a sample mean of 121. with a standard deviation of 14.1. The systolic blood pressure after exercising is 135.9, with a standard deviation of 18.1. Is there more variability in systolic blood pressure before exercise or after exercise

Answer 1

Yamelin,

 

Before exercising:   (st. dev/mean) = 14.1/121 = 0.1165  or 11.65 % 

 

After exercising:     (st. dev/mean) = 18.1/135.9 = 0.1332 or 13.32 % 

 

The variability or spread of a probability distribution about its mean value.  The above computations show that the "after exercising" standard deviation represents a bigger proportion of its mean value and is therefore wider or greater.