In a factory, we produce rods the length of which is planned to be 80cm. We assume that the length of the rods varies randomly having a normal distribution.

We pick a sample of 100 rods and measure the length of each. We have the results that the arithmetic mean of the sample is 82cm and the variance of the sample is 0,025cm2.

Test at significance level =0.05 the null hypothesis that the average length of the rods produced in the factory has the desired value of 80cm. The alternative hypothesis is that the average length differs from the desired value of 80cm.