If appropriate, create a 98% confidence interval estimate for the average test score of graduates with an overall average mark of 75, based on the data set described in Exercise 20.
In exercise
A large company has developed a written test to screen applicants, and the mark on this test has been a good predictor of employee suitability for the graduates that are hired. Because administering the test is time-consuming and costly, the company is wondering if it is worthwhile. One cheaper option is to rely on the overall average mark of the graduate as an indicator of suitability. An analyst has collected data on the overall average mark of a number of interviewees, and their scores (out of 70) on the company test. Create a scatter diagram for the data. Does it appear that there is a relationship between the two variables? Describe it, generally and mathematically.