Score-S-Up is a company that helps students improve their test scores on college

Question

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 simple random sample is taken of 15 students who took the course and the GMAT again. The average increase of the GMAT scores in the sample was 26 with a standard deviation of 5.4. What is the P-value of the test (rounded to 4 decimal places)?

Explanation / Answer

TS = (Xbar - mean)/sd/sqrt(n)

= (26 - 30)/(5.4/sqrt(15))

= -2.8688

df = n-1= 15

p-value = 2P(T < -2.8688)

= 0.01195

= 0.0120

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