statistics
posted by Lezlie .
The following frequency distribution presents a set of exam scores for a class of N= 20 students.
X F CF % C%
9099 4 20 20 100
8089 7 16 35 80
7079 4 9 20 45
6069 3 5 15 25
5089 2 2 10 10
a)Using interpolation find the 30th percentile.
The answer I came up with was 72.
B) FIND THE 88TH PERCENTILE
93.5
C) WHAT IS THE PERCENTILE RANK FOR X=77
40th percentile
D) WHAT IS THE PERCENTILE RANK FOR X=90
81st percentile
Are my answers correct. I did the % portion of the table myself. I'm not sure if I did it correctly though.
Thank You

I realize the table looks off. X= the scores 9395...etc. cf= 4,7,4,3,2,. %=20,35,20,15,10. c%=100,80,45,25,10.