Score-S-Up is a company that helps students improve their test scores on college entrance exams. They advertise that the study program increases a person's score on the GMAT by an average of 30 points. A consumer group wishes to test if the average score increase differs from 30 points. Assume the population distribution of increase in GMAT scores is approximately normal.
a) A simple random sample of 15 students who took the course and the GMAT again is taken. The average increase of the GMAT scores in the sample was 26 with a standard deviation of 5.4.
What is the value of the test statistic?
Use 3 decimal places.