The sick days of employees every two years in a company are normally distributed with a population standard deviation of 7 days and an unknown population mean. If a random sample of 20 employees is taken and results in a sample mean of 21 days, find a 95% confidence interval for the population mean.

Step-by-step explanation:

Let . . . ,Xn be the random sample of n employee's sick days. It is given that the random samples follows the  Normal distribution along with standard deviation of 7 days. Let

or  

So,

Therefore, the confidence interval of the population mean for α = 0.05 is

=

=

= (17.93, 24.07)

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step-by-step explanation: