A sample of 900 items is taken from a population with standard deviation 15. The mean of the sample is 25. Test whether the sample has come from a population with mean 26.8. Take a=5%

Answer 1

The null hypothesis is that the population mean is 26.8. The alternative hypothesis is that the population mean is not 26.8.

Using the z-test, the test statistic is calculated as:

z = (25 - 26.8) / (15 / √900) = -2.4

The critical value for a 5% significance level is -1.645. Since the test statistic is less than the critical value, we reject the null hypothesis and conclude that the sample has not come from a population with mean 26.8.