PSYC 354 Homework 6 Liberty University

Homework 6

Percentiles and Hypothesis Testing with Z-Tests

Be sure you have reviewed this module/week’s lessons and presentations along with the practice data analysis before proceeding to the homework exercises. Complete all analyses in SPSS, and then copy and paste your output and graphs into your homework document file. Number all responses. Answer any written questions (such as the text-based questions or the APA Participants section) in the appropriate place within the same file. Review the “Homework Instructions: General” document for an example of how homework assignments must look.

Part I: Concepts

For this module/week, this section comprises most of your assignment. For help working the percentile and z-score problems, refer to the presentations in this module/week on z-tables and percentages as well as hypothesis testing with z-tests.

1. 1.     Answer the following Nolan and Heinzen end-of-chapter questions for Chapter 7: 7.8, 7.18, 7.20, 7.22, 7.28 [sections (a) and (b)], 7.32 [sections (a)–(e)], 7.34, 7.39, and 7.40 [sections (a) and (b)]. If applicable, remember to show work in your homework document for partial credit.

7.8 What are the six steps of hypothesis testing?

7.39  Directional versus nondirectional hypotheses: For each of the following examples, identify whether the research has expressed a directional or a nondirectional hypothesis:

A.  A researcher is interested in studying the relation between the use of antibacterial products and the dryness of people’s skin.  He thinks these products might alter the moisture in skin compared to other products that are not antibacterial. 

B.  A student wonders if grades in a class are in any way related to where a student sits in the classroom.  In particular, do students who sit in the front row get better grades, on average, than the general population of students? 

C. Cell phones are everywhere, and we are now available by phone almost all of the time. Does this translate into a change in the closeness of our long-distance relationships? 

7.40  Null hypotheses and research hypotheses:  For each of the following examples (the same as those in Exercise 7.39), state the null hypothesis and the research hypothesis, in both words and symbolic notation:

a.  A researcher is interested in studying the relation between the use of antibacterial products and the dryness of people skin.  He thinks these products might alter the moisture in skin compared to other products that are not antibacterial. 

b.  A student wonders if grades in a class are in any way related to where a student sits in the classroom.  In particular, do students who sit in the front row get better grades, on average, than the general population of students?

2. Fill in the blank with the best word or words.

a.     Values of a test statistic beyond which you reject the null hypothesis are called ________.

b.     The ___________ is the area in the tails in which the null can be rejected.

c.     If your data differ from what you would expect if chance were the only thing operating, you would call your finding ___ _______.

d.     A hypothesis test in which the research hypothesis is directional is a(n) _______ test.

e.     A hypothesis test in which the research hypothesis specifies that there will be a difference but does not specify the direction of that difference is a(n) ________ test.

If your z-statistic exceeds the critical cutoff, you can _____________ the null hypothesis.

3. The police department of a major city has found that the average height of their 1,250 officers is 71 inches (in.) with  = 2.3 inches. 

4. The verbal part of the Graduate Record Exam (GRE) has a  of 500 and  = 100. Use the normal distribution to answer the following questions

Part II: SPSS Analysis

1. 1.     For this problem, you will be using last module/week’s data set containing IQ scores. Open the file; it will also contain the standardized IQ variable you created last module/week.
   1. a.     Using the z-scored IQ variable, create percentile ranks assuming the scores are normally distributed. Call the new percentile variable “IQ rank.”

1. b.     List the first 5 IQ ranks from your file (rows 1–5).