Introduction to Sociological Research_Kupchik_Date__041610

Introduction to Sociological Research_Kupchik_Date__041610...

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When we want to compare means of a continuous variable (measured on either an interval or ratio level) across two independent groups, we perform an independent samples t-test. For example, we may be comparing the average incomes across a sample of female attorneys and a sample of male attorneys. Our significance test tells us whether the difference between groups that we see in our sample is likely due to only chance sample variation, or due to actual differences between the two groups’ population values. As usual, we begin with our null hypothesis and alternative hypothesis. Since we are testing whether the two sample means are significantly different from one another, for a
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Unformatted text preview: two-tailed test: H : 1 = 2 H 1 : 1 2 . We decide on alpha, and we find the critical value of t (t critical ) for degrees of freedom n 1 +n 2-2. We will only use the t-distribution (not the z-distribution). We then compute t calculated . If we assume that our population standard deviations are not equal across the two populations, then we use this formula: Finally, we compare t calculated to t critical . If t calculated is farther from 0 than t critical then we reject the null hypothesis. 1 1 2 2 2 1 2 1 2 1-+--= n s n s x x t CALCULATED...
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