The t value for the test statistic is (22.314-22)/(20/√28)=0.0831 approx. The number of degrees of freedom is 28-1=27. The critical value for a significance level of 0.05 for this is 1.703 for a 1-tail test (because we are testing an inequality standard deviation<22 seconds, the null hypothesis claim). Null hypothesis is the stated claim; the alternative hypothesis is that the standard deviation is greater than or equal to 22 seconds. 0.0831 is less than the critical value, so we reject the null hypothesis and by default conclude that the standard deviation is greater than or equal to 22 seconds with a confidence of 95%.