# PYCH 625 Week 2 Practice

*University of Phoenix Material*

*Time to*

Practice – Week TwoPractice – Week Two

**Complete**Parts A,

B, and C below.

Part A

1. Why is a

*z*

score a standard score? Why can standard scores be used to compare scores from

different distributions?

2. For the following set of scores, fill in the

cells. The mean is 74.13 and the standard deviation is 9.98.

Raw score

*Z*score

68.0

?

?

–1.6

82.0

?

?

1.8

69.0

?

?

–0.5

85.0

?

?

1.7

72.0

?

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?

b. What

is the probability of a score falling above a raw score of 80?

c. What

is the probability of a score falling between a raw score of 81 and 83?

d. What

is the probability of a score falling below a raw score of 63?

4. 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?

From

Salkind (2011). Copyright © 2012 SAGE. All Rights Reserved. Adapted with

permission.

Part B

The

questions in Part B require that you access data from Using

SPSS for Windows and Macintosh. This data is available on the

student website under the Student Text Resources link.

The

data sets for problems 5 and 6 can be found through the Pearson Materials in

the Student Textbook Resource Access link, listed under Academic Resources. The

data is listed in the data file named Lesson 20 Exercise File 1. Answer Exercises 5

and 6 based on the following research problem:

Ann

wants to describe the demographic characteristics of a sample of 25 individuals

who completed a large-scale survey. She has demographic data on the

participants’ gender (two categories), educational level (four categories),

marital status (three categories), and community population size (eight

categories).

5. Using

IBM® SPSS® software, conduct a frequency analysis on the

gender and marital status variables. From the output, identify the following:

a. Percent

of men

b. Mode

for marital status

c. Frequency

of divorced people in the sample

6. Using

IBM® SPSS® software, create a frequency table to

summarize the data on the educational level variable. Copy and paste the output

from IBM® SPSS® into this worksheet.

7. The

data set for this problem can be found through the Pearson Materials in the

Student Textbook Resource Access link, listed under Academic Resources. The

data is listed in the data file named Lesson 21 Exercise File 1. David collects

anxiety scores from 15 college students who visit the university health center

during finals week. Compute descriptive statistics on the anxiety scores. From

the output, identify the following:

a. Skewness

b. Mean

c. Standard

deviation

d. Kurtosis

From Green

& Salkind (2011). Copyright © 2012 Pearson Education. All Rights Reserved.

Adapted with permission.

Part C

**Complete**the questions below. Be specific and provide examples when relevant.

**Cite**any sources consistent with APA guidelines.

Question

Answer

What is

the relationship between reliability and validity? How can a test be reliable

but not valid? Can a test be valid but not reliable? Why or why not?

How does

understanding probability help you understand statistics?

How could

you use standard scores and the standard distribution to compare the reading

scores of two students receiving special reading resource help and one

student in a standard classroom who does not get special help?

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?

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