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Chi Square

Two chi square tests. Goodness of fitOne variableDetermines how well the sample proportions match a pre-specified distributionIndependenceTwo variablesDetermines whether there is a relationship between two variables. Test for independence. Each person is classified on two separate variables E

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Chi Square

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    1. Chi Square

    2. Two chi square tests Goodness of fit One variable Determines how well the sample proportions match a pre-specified distribution Independence Two variables Determines whether there is a relationship between two variables

    3. Test for independence Each person is classified on two separate variables Examples (1) littering condition and (2) littering behavior (1) gender and (2) hair color (1) gender and (2) facial expression

    4. Steps in hypothesis testing State the hypotheses null research Select an alpha level and determine the critical value Compute the test statistic Make a decision

    5. Test for independence Null hypothesis There is no difference between population proportions The distribution of proportions for one group/condition does not differ from the distribution of proportions of another group/condition There is no relationship between two variables

    6. Test for independence Null hypothesis (H0): There is no relationship between two variables. The distribution of proportions for one group/condition does not differ from the distribution of proportions of another group/condition. Research hypothesis (H1): There is a relationship between the two variables. The distribution of proportions for one group does differ from the distribution of another group.

    7. Example littering (Cialdini et al., 1990).

    8. Littering study Null hypothesis There is no relationship between the amount of existing litter and littering behavior. The proportion of people littering will not differ across the three litter conditions. Research hypothesis (Nondirectional) There is a relationship between the amount of existing litter and littering behavior. (Nondirectional) The proportion of people littering will differ across the three litter conditions. (Directional) The proportion of people littering will increase as the amount of existing litter increases.

    9. Test for independence Degrees of freedom (df) df = (R 1)(C 1) R = the number of rows C = the number of columns

    11. Test for independence Degrees of freedom (df) df = (R 1)(C 1) R = the number of rows C = the number of columns Rows = 2 Columns = 3 df = (2 1)(3 1) = 2

    12. Critical values for chi square distribution

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