stores in high promotion condition have higher average sales than stores in

Stores in high promotion condition have higher

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stores in high promotion condition have higher average sales than stores in other conditionsReason: rejecting the null simply means that at least the average for one group is different from others, but didn’t say which group43
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15Tests of Differences 1. One Sample 2. Two Independent Samples 3. Paired Samples 4. More Than Two Samples Which test to use? It depends on (1). the number of variables and (2). Number of groups involved t tests ANOVA 44 One-Sample t-test One sample Independent Samples t-test Two independent samples Paired samples t-test Two dependent samples ANOVA Two or more samples Summary Average temperature in August = 17 ° Sales in store A = Sales in store B Knowledge of statistics after class = before class Average fuel prices in suburbs A,B and C are different 45 Side topic - some further clarification of the distinction between relational and comparative RQs 46
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16 47 So far we have suggested that there is a close correspondence between the type of RQ and statistical tests used Hypothesis Testing Test of Association (relational RQ) Test of Differences (comparative RQ) Means Proportions Different forms of t test/ANOVA Cross tabulation Correlation Multiple regression 48 It is important to recognize that the distinction is artificial and sometimes not so clear-cut Examples of a relational RQ 1.Does genderaffect how frequently people eat fast-food? 2.Does education attainmentaffect how frequently people eat fast-food? 1.Do men and women differ in how frequently they eat fast-food? 2. Does the frequency of fast-food consumption differ across people of different levels of education ?111 49 What characterizes these types of RQ is that the independent variable (IV) is a categorical variable while the dependent variable (DV) is metric Example Does education attainment affect how frequently people eat fast-food ? There is no test of association for this type of RQ (for test of associations both variables need to be categorical or metric, but not one of each type) What you need to do is to first re-phrase the relational RQ as the corresponding comparative RQ and then choose the corresponding test of differences (an independent-samples t test or one-way ANOVA) IV is categorical DV is metric
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17 Today’s agenda 50 Hypothesis testing – tests of differences Different types of t tests Two-tailed vs. one-tailed test – ANOVA How to write about hypothesis testing A few words on assignment 2 How to write about hypothesis testing – the formulaic approach • 1 st step – describe the test – Which test did you use? – What variables are involved? What are the groups involved?
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