## Elementary Statistics (12th Edition)

The sample size is more than 25, hence the value of the test statistic: $z=\frac{(x+0.5)-n/2}{\sqrt n/2}=\frac{(5+0.5)-27/2}{\sqrt{ 27}/2}=-3.08.$ By using the table, the corresponding critical value: $z=\pm 1.96.$ If the value of the test statistic is in the rejection region, we reject the null hypothesis. -3.08 is less than -1.96 hence we reject the null hypothesis, hence there is a difference.