lab5_ttest - ttest TestingInferences aboutPopulation Means...

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    t -test Testing Inferences  about Population  Means
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    Learning Objectives Compute by hand and interpret Single sample  t Independent samples  t Dependent samples  t Use SPSS to compute the same tests  and interpret the output
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    Review 6 Steps for Significance  Testing 1. Set alpha (p level). 2. State hypotheses,  Null and Alternative. 3. Calculate the test  statistic (sample  value). 1. Find the critical  value of the statistic. 2. State the decision  rule. 3. State the  conclusion.
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    One Sample Exercise (1) 1. Set alpha.    α  = .05 2. State hypotheses.   Null hypothesis is H 0 μ  = 1000. Alternative hypothesis is H 1 μ    1000. 3. Calculate the test statistic Testing whether light bulbs have a life of 1000  hours
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    Calculating the Single Sample t 800 750 940 970 790 980 820 760 1000 860 What is the mean of our sample?  =  867 What is the standard deviation for  our sample of light bulbs? SD= 96.73 35 . 4 59 . 30 1000 867 - = - = - = X X S X t μ 59 . 30 10 73 . 96 = = = N SD SE X
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    Determining Significance 1. Determine the critical value.  Look up in  the table (Heiman, p. 708).  Looking for  alpha = .05, two tails with df = 10-1 = 9.   Table says 2.262. 2. State decision rule.  If absolute value of  sample is greater than critical value,  reject null.              If |-4.35| > |2.262|,  reject H 0 .
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  Stating the Conclusion 6.  State the conclusion.  We reject the null  hypothesis that the bulbs were drawn from a  population in which the average life is 1000 hrs.  The difference between our sample mean (867)  and the mean of the population (1000) is SO  different that it is unlikely
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This note was uploaded on 05/21/2011 for the course PSY 3213 taught by Professor Staff during the Fall '08 term at University of South Florida - Tampa.

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lab5_ttest - ttest TestingInferences aboutPopulation Means...

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