Question

A telecommunications company commissioned a study to investigate the amount of time that people spend on phone calls. The study that found that the length of time that people spend on a phone call is approximately normally distributed with a mean of 425 seconds and a standard deviation of 73.1 seconds.

Calculate the standardized value (z) for a time of 250 seconds. Give your answer to 2 decimal places.

Answer 1

Answer

We have population mean

population standard deviation

we have to find the standardized value z for a time of 250 seconds, i.e.

Using the formula for z score, we get

setting the given values, we get

So, required z value is -2.39