Asked by Anonymous

The scatter diagram of midterm scores and final scores in a large class is football shaped. For about 80% of the students, the regression estimate of final score based on midterm score is correct to within 15 points. For about 95% of the students, the regression estimate of final score based on midterm score is correct to within how many points?
Answered by Friend anonymous
It has to be 21
Answered by helpus
why 21?
Answered by xstatistics
22.95
Answered by EDXProfessor
80% is between -1.2815 and 1.2815 in standard units
90% is between -1.96 and 1.96

15/r.m.s. error = 1.2815
score/r.m.s. error = 1.96

=> score = 15*1.96/1.2815

Now, when rounding 1.2815 to either 1.281 or 1.282 you'll get slightly different result