PSYCH/625 Statistics class

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University of Phoenix Material

Time to Practice – Week Two

Complete Part A,

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.

Why is a z score a standard score? Why can standard scores be used to compare scores from different distributions?
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	?
?	–1.6
82.0	?
?	1.8
69.0	?
?	–0.5
85.0	?
?	1.7
72.0	?

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.

What is the probability of a score falling between a raw score of 70 and 80?
What is the probability of a score falling above a raw score of 80?
What is the probability of a score falling between a raw score of 81 and 83?
What is the probability of a score falling below a raw score of 63?

Jake needs to score in the top 10% in order to earn a physical fitness certificate. The class mean is 78 and the standard deviation is 5.5. What raw score does he need?
Who is the better student, relative to his or her classmates? Use the following table for information.

Math
Class mean	81
Class standard deviation	2
Reading
Class mean	87
Class standard deviation	10
Raw scores
	Math score	Reading score	Average
Noah	85	88	86.5
Talya	87	81	84
Z-scores
	Math score	Reading score	Average
Noah
Talya

In a standard normal distribution: What does a z score of 1 represent? What percent of cases fall between the mean and one standard deviation above the mean? What percent fall between the mean and –1 to +1 standard deviations from the mean? What percent of scores will fall between –3 and +3 standard deviations under the normal curve?