University of Phoenix Material
Time to Practice – Week Two
Complete Parts A, B, and C below.
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?
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 
? 
? 
–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?
5. 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 
Zscores 




Math score 
Reading score 
Average 
Noah 



Talya 



6. 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
7. 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.
8. 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
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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