Researchers have conducted a survey of 1600 coffee drinkers asking how much coffee they drink in order to confirm previous studies. Previous studies have indicated that 72% of Americans drink coffee. The results of previous studies (left) and the survey (right) are below. Observed Expectaed (O-E)^2 Response O E 2 cups per week 206 240 1156 1 cup per week 193 208 225 1 cup per day 462 432 900 2+ cups per day 739 720 361 Calculate the test statistic at ? = 0.10. a. -8.4831 b. non of them c. 9.4831 d. 8.4831 e. -9.4831
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The formula for the chi-square test statistic is: χ² = Σ [ (O - E)² / E ] where: O = observed frequency, Show more…
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Researchers have conducted a survey of 1600 coffee drinkers asking how much coffee they drink in order to confirm previous studies. Previous studies have indicated that 72% of Americans drink coffee. The results of previous studies (left) and the survey (right) are below. Response | Observed O | Expected E | (O - E)² --- | --- | --- | --- 2 cups per week | 206 | 240 | 1156 1 cup per week | 193 | 208 | 225 1 cup per day | 462 | 432 | 900 2+ cups per day | 739 | 720 | 361 Is there enough evidence to conclude that the distributions are the same at α = 0.10? a. there is no enough statistical evidence to reject H₀. b. there is no enough statistical evidence to accept Hₐ. c. non of them d. there is enough statistical evidence to reject H₀.
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Coffee: A Study on the Number of Cups Consumed by U.S. Adults A researcher claims that the number of cups of coffee U.S. adults drink per day is distributed as shown in the figure. You randomly select 1600 U.S. adults and ask them how many cups of coffee they drink each day. The table below shows the results. At a significance level of α = 0.05, test the researcher's claim. How many cups of coffee do you drink per day? Survey Results: Response Frequency, f 0 cups 570 1 cup 432 2 cups 282 3 cups 152 4 or more cups 164 About 64% of Americans drink at least 1 cup per day.
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Researchers wanted to determine if there was an association between daily coffee consumption and the occurrence of skin cancer. The researchers looked at 93,676 women enrolled in the Women's Health Initiative Observational Study and asked them to report their coffee-drinking habits. The researchers also determined which of the women had nonmelanoma skin cancer. After their analysis, the researchers concluded that consumption of six or more cups of caffeinated coffee per day was associated with a reduction in nonmelanoma skin cancer. Source: European Journal of Cancer Prevention, $16(5): 446-$ $452,$ Octobcr 2007 (a) What type of observational study was this? Explain. (b) What is the response variable in the study? What is the explanatory variable? (c) In their report, the researchers stated that "After adjusting for various demographic and lifestyle variables, daily consumption of six or more cups was associated with a $30 \%$ reduced prevalence of nonmelanoma skin cancer." Why was it important to adjust for these variables?
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