Question

1. Over a five-year period, 375 undergraduates have taken statistics during the fall and spring in our department. The overall final exam average is 80.50, with a standard deviation of 9.20. Using the normal curve table in the back of your textbook, answer the following:
(a) What is the percentile rank of someone scoring 84?  

Answer 1

Given information,

Someone scoring 84

x =84   and n = 1

Percentile rank formula = 100*P(X< 84 )

Z score formula :

P( X < 84 ) = P( Z < 0.38) = 0.6480      ( we find this using Z table check 0.3 row and 0.08 column)

Percentile rank

100*P(X<84 ) = 100*0.6480 = 64.80 ~ 65     (64.80 which is approximately 65)

The percentile rank of someone scoring 84 is 65