raw score

Time to Practice Week Two

July 28, 2014

PSY 625

University of Phoenix Material

Time to Practice – Week Two

Complete Parts A, B, and C below.

Part A

Some questions in Part A require that you access data from Statistics for People Who (Think They) Hate Statistics. This data is available on the student website under the Student Text Resources link.

1. Why is a z score a standard score? Why can standard scores be used to compare scores from different distributions?

A z score is considered a standard score because it is based on the degree of variability within its distribution. Standard scores across different distributions measure in the same fashion. A z score is the result of dividing the amount that a raw score differs from the mean of the distribution by the standard deviation. So, scores below the mean will have negative z scores, and scores above the mean will have positive z scores. Positive z scores always fall to the right of the mean, and negative always fall to the left (Salkind, 2011).

2. For the following set of scores, fill in the cells. The mean is 70 and the standard deviation is 8.

Raw score	Z score
68.0	-0.25
57.2	–1.6
82.0	1.5
84.4	1.8
69.0	–0.125
66.0	–0.5
85.0	1.875
83.6	1.7
72.0	.25

3. Questions 3a through 3d are based on a distribution of scores with  and the standard deviation = 6.38. Draw a small picture to help you see what is required.

a. What is the probability of a score falling between a raw score of 70 and 80? 0.5668

b. What is the probability of a score falling above a raw score of 80? 0.2166

c. What is the probability of a score falling between a raw score of 81 and 83? 0.0686

d. What is the probability of a score falling below a raw score of 63? 0.0300