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Unformatted text preview: Chi-square test for goodness-of-fit Situation: We want to know if a frequency follows the claimed distribution. We will use a chi-square test for goodness-of-fit. Example: Companies A and B conducted aggressive advertising campaigns to increase their respective share of the market. Before the advertising campaign began, the market share of the company A was 45%, whereas company B had 40%. Other competitors had the remaining 15%. To determine if these market shares changed after the advertising campaign, a marketing analyst solicited the preference of a random sample of 200 customers. Of the 200 customers, 102 preferred company As product, 82 preferred company Bs product, while the remaining 16 preferred the products of one of the competitors. Can the analysts infer at the 5% significance level that customer preference has changed? Solution: Step1 H : p 1 =0.45, p 2 =0.40, p 3 =0.15 H A : At least one p i is not equal to its specified value Step 2 Assuming that H is true, the calculated chi-square value is given by:...
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This note was uploaded on 04/07/2008 for the course DSCI 232 taught by Professor Zhang during the Spring '08 term at CofC.
- Spring '08