REVIEW EXERCISES 95 6. Among applicants to one law school, the average LSAT scor

Question

REVIEW EXERCISES 95 6. Among applicants to one law school, the average LSAT score was about 169, the SD was about 9, and the highest score was 178. Did the LSAT scores follow the normal curve? 7. Among freshmen at a certain university, scores on the Math SAT followed the normal curve, with an average of 550 and an SD of 100. Fill in the blanks; (a) A student who scored 400 on the Math SAT was at theth per- (b) To be at the 75th percentile of the distribution, a student needed a score explain briefly centile of the score distribution. of about points on the Math SAT. 8. True or false, and explain briefly- (a) If you add 7 to each entry on a list, that adds 7 to the average. (b) If you add 7 to each entry on a list, that adds 7 to the SD. (c) If you double each entry on a list, that doubles the average. (d) If you double each entry on a list, that doubles the SD (e) If you change the sign of each entry on a list, that changes the sign of the average. (0 If you change the sign of each entry on a list, that changes the sign of the SD

Explanation / Answer

6. Solution:- impossible, For example the normal curve says that about 16% of the scores should be more than 1 SD below the average, and none are. i.e.the score more than 169+9 = 178.178 is the highest one.

7. solution:- mean = 550,sd = 100

a) Z = (400 - 550) / 100 = -1.5

Now look up -1.5 on a Z table. We get about 7 percent.

  
b) This time we start by finding the Z value at 75 percent. It is 0.6745.

0.6745 = (X - 550) / 100

First multiply through by 100.

67.45 = X - 550

=> 67.45 + 550 = X

=> X = 617.45 points

8 solution:-
a) True
  
b) Flase

C) True

d) True

e) True

f) flase

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