1. For the following set of scores, find the value of ach expression:

X

6

-1

0

-3

-2

a. ∑X

b. ∑X²

c. ∑(x+3)

2. The following frequency distributionpresents a set of exam scores for class of n=20 students.

X

6

-1

0

-3

-2

X f cf c%

90-99 4 20 100

80-89 7 16 80

70-79 4 9 45

60-69 3 5 25

50-59 2 2 10

A. find the 30th percentile

B. find the 88 percentile

C. what is the percentilerank for x=77

D. what is the percentile rank for x=90

Please see the attached file.

Qk = L+w/fk*(kn-cfb)

Where

Qk = the kth percentile

L = lower limit of the class interval that includes the kth percentile

n = total frequency

cfb = …

Two problems are solved dealing with chi-squared distributions and percentile ranks.