18.1 Chi-Squared Tests

Table 18.1 summarizes purchases at Amazon made by a sample of 555 visitors of varying income who bought either a camera or a mobile phone (but not both).

Table 18.1 Contingency table of purchase category versus household income.

Household Income Total
Less than $25,000 $25,000 to $49,999 $50,000 to $74,999 $75,000 to $99,999 $100,000 or more
Purchase Category Camera 26 38 76 57 50 247
Phone 72 76 73 34 53 308
Total 98 114 149 91 103 555

The association evident in this contingency table suggests that income and choice are dependent. Households with lower incomes are more likely to purchase a phone, whereas higher-income households are more likely to purchase cameras. Almost 3/4 of those with estimated ...

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