Statistics Question

Question

If the average (mean) mid-twenties male weighs 167 pounds and a weight of 153 is in the 31st percentile, what is the standard deviation of the weights in this age group

Answer 1

Using a standard normal table and looking up what z value corresponds to an area of .31, we find that the z value is -.49585

 

We also note that z = (x-mean)/standard deviation

 

Solving for standard deviation gives us,

 

standard deviation = (x-mean)/z = (153 - 167)/-.49585 = 28.23