This is a sample from the Farmington Heart Study. Physicians are interested in s

Question

This is a sample from the Farmington Heart Study. Physicians are interested in studying the effects of obesity on health. Nationally, 37.8% of people in the US are obese. Determine if the proportion of people in this studies population differs from the rest of the country by calculating the proportion and two-sided 95% confidence interval for this sample. H31 Date OBESE IT n No 3860 87.05% 574 12.95% Yes n Grand Total 4434 100.00% 9 This is a sample from the Framin 10 Physicians are interested in study 12 Nationally, 37.8% of people in the Determine if the proportion of peo the country by calculating the pran

Explanation / Answer

Null Hypothesis: The proportion of people in this studies population differs from the rest of the country

Alternate Hypothesis: The proportion of people in this studies population is not differing from the rest of the country

Obese

Yes

No

Expected

37.8%

62.2%

From the study

12.95%

87.05%

Chi-Squared test is performed using the equation= (Observed-Expected)2/Expected

X2=(12.95-37.8) 2/37.8+(87.05-62.2) 2/62.2=16.3+9.93=26.2

Degrees of freedom=2-1=1

For 95% confidence interval for this sample, the obtained chi square value (26.2) is larger than the critical chi square value (3.841), thus we can reject the null hypothesis and we can say that 95% confidently that the people from this study is not differing from the rest of the country.

Obese

Yes

No

Expected

37.8%

62.2%

From the study

12.95%

87.05%

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