Sixteen undergraduate students were randomly selected from a university and their systolic blood pressure was tested. The sample mean and standard deviation were 114.6 mmHg and 10.8 mmHg respectively. Supposing that you are asked to test hypotheses H_o: = 120 versus H₁: < 120.

a. What is the obtained t-score, the value of the test statistic obtained from the sample, under the null hypothesis?

b. What is the number of degrees of freedom of the obtained t-statistic?

c. What would be the decision rule if the level of significance is .05?