# 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?

#### 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?

STATISTICS FOR PEOPLE WHO (THINK THEY) HATE STATISTICS.

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
Class mean 87
Class standard deviation 10
Raw scores
Noah 85 88 86.5
Talya 87 81 84
Z-scores
Noah
Talya

Part B

Some 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 for Exercises 6 and 7 are in thedata file named Lesson 20 Exercise File 1. Answer Exercises 6 and 7 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).

Using IBM® SPSS® software, conduct a frequency analysis on the gender and marital status variables. From the output, identify the following:

Percent of men
Mode for marital status
Frequency of divorced people in the sample

Using IBM® SPSS® software, create a frequency table to summarize the data on the educational level variable.

The data for Exercise 8 is available 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:

Skewness
Mean
Standard deviation
Kurtosis

Part C

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

Cite any sources consistent with APA guidelines.