Answers the Question: Are the populations in question significantly different with regard to a particular distribution? This means you’re considering more than one population 13-2 Chi-Square for Homogeneity

Answers the Question: Are the populations in question significantly different with regard to a particular distribution? In other words, are they “homogeneous”? Chi-Square for Homogeneity

For Degrees of Freedom, df = (c-1)(r-1) –c = the number of columns –r = the number of rows Chi-Square for Homogeneity

For Degrees of Freedom, df = (c-1)(r-1) –c = the number of columns –r = the number of rows Conditions: –All Expected cells must be at least 1 –Not more than 20% of all Expected cells can be less than 5 Chi-Square for Homogeneity

Major fistfight in the S.B. around 1900! –Pearson: df = cells - 1 –Fisher: df = (c-1)(r-1) Chi-Square for Homogeneity

Observed Expected NoYesNoYes Desipramine Lithium Placebo Example from Text—Cocaine Addiction

Chi-Square for Homogeneity ObservedCounts NoYes Desipramine Lithium Placebo Example from Text—Cocaine Addiction

Create the test statistic just as before, only now use all cells :Create the test statistic just as before, only now use all cells :

Chi-Square for Association (or Independence) Now we ask the question, “Within one population, are two variables associated with one another, or are they independent? –Ho becomes: “There is no association between the two variables” (i.e., the variables are independent) –Ha becomes: “There is an association between the two variables”

Bears getting sick from various reasons: Coastal Grizzlies Other Grizzlies Bad Berries 2428 Bad Fish 718 Bad People 1612 Coastal Grizzlies Inland Grizzlies Bad Berries2428 Bad Fish718 Bad People1612