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Sat 16 Jun, 2012 09:04 am
1. A study examined whether adding a fragrance to a window cleaner led people to believe that it cleans better than an unscented product. There were 12 subjects in each group: scented or unscented. The mean cleaning effectiveness rating for the group getting the scented cleaner was 7.42. The mean cleaning effectiveness rating for the group getting the unscented cleaner was 6.00. The standard deviation for cleaning effectiveness ratings across all subjects was 1.369. A t test showed that the scented cleaner was rated as a significantly more effective cleaner (p < .01).
a. Calculate the Cohen’s d effect size for this study:
b. Interpret the result: Do you believe there was a practical difference in cleaning effectiveness between scented and unscented cleaners? Explain your answer.
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