Lab4 - STAT 350 Lab #4 t Tests SOLUTION For all tests...

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Knapp – Stat 350 Lab #4: Page 1 of 11 STAT 350 Lab #4 – t Tests SOLUTION For all tests below, use a significance level of 0.05. 1. Conduct the analyses for the following problem using Minitab. 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. Give a side-by-side box plot of the two groups (two box plots on a single figure – they must have the same scale to be meaningful!) old young 160 150 140 130 120 110 100 90 80 70 Data Boxplot of young, old A boxplot of the data is also provided automatically when you test for equal variances (see part c) – this would also be an acceptable boxplot for this part.
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Lab #4: Page 2 of 11 c. Determine whether a t -test assuming equal variances is appropriate or not. Paste the appropriate figure onto your assignment. Clearly state your conclusion. young old 40 30 20 10 0 95% Bonferroni Confidence Intervals for StDevs young old 160 140 120 100 80 Data Test Statistic 0.04 P-Value 0.001 Test Statistic 5.19 P-Value 0.034 F-Test Levene's Test Test for Equal Variances for old, young Based on either the F -test or Levene’s Test, the assumption of equal variances is not appropriate. d. Based on your responses to parts (a) and (c) conduct the appropriate t -test, and copy and paste the output of the analysis onto your assignment. Two-Sample T-Test and CI: old, young Two-sample T for old vs young N Mean StDev SE Mean old 7 122.71 4.96 1.9 young 15 114.1 24.3 6.3 Difference = mu (old) - mu (young) Estimate for difference: 8.58 95% lower bound for difference: -2.86 T-Test of difference = 0 (vs >): T-Value = 1.31 P-Value = 0.104 DF = 16 e. What was the mean SSHA score for the younger students? What was the mean SSHA score for the older students? younger students:
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This note was uploaded on 03/09/2010 for the course STAT 350 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.

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Lab4 - STAT 350 Lab #4 t Tests SOLUTION For all tests...

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