Lecture_5 T – Tests

Lecture_5 T – Tests - Lecture4 TTests...

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    Lecture 4 T – Tests Tuesday February 16 th 10:10 – 11:00am Change is the watchword of progression. When      We tire of well-worn ways, we seek for new. This restless craving in the souls of men      Spurs them to climb, and seek the mountain view. - Ella Wheeler Wilcox
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    Today’s Outline One Sample T-Tests One Sided Hypotheses Two Sided Hypotheses Two Sample T-Tests One Sided Hypotheses Two Sided Hypotheses What about SAS 9.2?
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    Quick Notes for Local Paths When accessing local paths while using SAS remotely (computer labs), You CAN use local drives by using the keyword: \\tsclient libname stat200 "\\tsclient\I\Stat480\HW4\" ; (This would allow you to use a USB key to hold everything.) Local Drive Letter
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    One-Sample T-Tests
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    Specify the Hypotheses Does the average student exercise more than 3 hours per week? H 0 H A Null Hypothesis Alternative Hypothesis What we want to Disprove What we want to Prove
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    > Specify the Hypotheses Does the average student exercise more than 3 hours per week? H 0 H A µ Hours of Exercise µ Hours of Exercise 3 ? ?
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    One Sample Test How do we translate the hypotheses into SAS code? Proc ttest data =stat200.complete; var HrsExer; run ; SAS will only perform a two-sided test.
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    One Sample Test Don’t forget to specify the null value, if it’s different from 0.0. Proc ttest data =stat200.complete H0 = 3.0 ; var HrsExer; run ;
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    One-Sample T-Test Output The TTEST Pr ocedur e Var i abl e: Hr sExer N Mean St d Dev St d Er r M i ni mum Maxi mum 997 5. 1404 3. 9225 0. 1242 0 20. 0000 95% CL Mean St d Dev CL St d Dev 4. 8966 5. 3842 3. 7576 4. 1027 DF t Val ue Pr > | t | 996 17. 23 <. 0001
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    Convert from 2-sided to 1-sided Is mean on same side as alternative hypothesis? If so , then p-value = ( 2-sided p-value ) / 2.0 If not , then p-value = 1.0 – ( 2-sided p-value ) / 2.0
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    Convert from 2-sided to 1-sided 1. Is mean on same side as alternative hypothesis?
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Lecture_5 T &amp;acirc;€“ Tests - Lecture4 TTests...

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