# l4 - STAT 350 Fall 2008 DUE Monday October 20th the...

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STAT 350 – Fall 2008 Lab #4 DUE: Monday, October 20 th @ the beginning of class All the following analyses should be conducted using SAS. For all tests, use a significance level of 0.05. Attach the SAS input (editor window content) at the end of your assignment. 1. The Survey of Study Habits and Attitudes (SSHA) is a psychological test that measures students' study habits and attitude toward school. Scores range from 0 to 200. Higher scores indicate better attitudes. An educational psychologist believes that older students have a better attitude toward school than younger students. To test this theory, she gives the SSHA test to 15 students with ages between 18 and 21 and to 7 students with ages between 30 and 40. She brings the results of their tests (below) to you for help with the analysis. young: 115 124 90 118 116 157 127 80 119 124 86 79 161 108 108 old: 116 122 127 131 122 119 122 a. State the null and alternative hypotheses. If you use subscripts, be clear to identify which group is which. H 0 : μ old - μ young = 0 H a : μ old - μ young > 0 b. Conduct a t -test, and copy and paste the output of the analysis onto your assignment. The TTEST Procedure Statistics Lower CL Upper CL Lower CL Upper CL Variable age N Mean Mean Mean Std Dev Std Dev Std Dev Std Err score old 7 118.13 122.71 127.3 3.1942 4.957 10.916 1.8736 score young 15 100.66 114.13 127.61 17.811 24.328 38.367 6.2814 score Diff (1-2) -11.03 8.581 28.188 15.71 20.534 29.653 9.3993 T-Tests Variable Method Variances DF t Value Pr > |t| score Pooled Equal 20 0.91 0.3722 score Satterthwaite Unequal 16.3 1.31 0.2087 Equality of Variances Variable Method Num DF Den DF F Value Pr > F score Folded F 14 6 24.09 0.0008 Lab #4 Page 1 of 6

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c. Is the assumption of equal variances appropriate? Give both the appropriate p -value and your conclusion. No, the assumption of equal variances is NOT appropriate.
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## This note was uploaded on 02/23/2009 for the course STAT 350 taught by Professor Staff during the Fall '08 term at Purdue.

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l4 - STAT 350 Fall 2008 DUE Monday October 20th the...

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