Question

Lengths of pregnancies​ (in humans) have a mean of 267.6 days and a standard deviation of 15.4 days. A woman tracked her pregnancy and found it to be 309 days. Find the z score for 309 days. Is such a length​ unusual?

Answer 1

The z-score is
`z = 2.65`

The length of days is not unusual

Explanation:

From the question we are told that

The population mean is
`\mu = 267.6 \ days`

The standard deviation is
`\sigma = 15.4 \ days`

The value considered is
`x = 309 \ days`

The z-score is mathematically represented as

`z = (x - \mu)/(\sigma )`

`z = (309 - 267.6)/(15.6 )`

`z = 2.65`

Now given that the z-score is not greater than 3 then we can say that the length of days is not unusual

(reference khan academy)