Based on the previous record, the average IQ for students at a university is 90 with a standard deviation is 15. A lecturer believes that this value has changed. He decided to conduct an IQ test and...

Based on the previous record, the average IQ for students at a university is 90 with a standard deviation is 15. A lecturer believes that this value has changed.
He decided to conduct an IQ test and 30 students are chosen at random. After the analysis
of the results, he found out that the average IQ for the sample is 85. Is there any evidence
to suggest that the average IQ has changed? Carry out the hypothesis test at level of
significance, α = 0.02 using
a) classical approach. Determine the critical value by sketching the normal curve.
b) p-value approach