Suppose you are reading a study conducted in the year 2000 about adolescent girls with anorexia nervosa in the United States. The study consisted of a random sample of 121 adolescent girls with anorexia nervosa, and provides summary statistics about various demographic characteristics of the sample, including home location by region of the country (West, South, Midwest, Northeast). You wonder whether the geographic distribution among adolescent girls with anorexia nervosa matches the geographic distribution of the US population. You obtain the following data from the 2000 census
Percent Distribution of the uS Population by Region
Region
West South Midwest Northeast
22.88% 22.46% 35.62% 19.04%
[Source: Hobbs F., & Stoops, N. (2002). Census 2000 special reports: Demographic trends in the 20th century. US Census Bure.] You use a chi-square test for goodness of fit to see if the distribution among adolescent girls with anorexia nervosa is the same as the distribution among all Americans, as described by the census data. Your data satisfies the requirements for a chi-square test. You conduct the test using a = .05 and reject the null hypothesis. You conclude there is a significant difference between the distribution of where the adolescent girls live and the distribution of the US population as provided by the census data The following table shows the hypothetical results of the study. This table displays the observed frequencies in the sample of adolescent girls with anorexia nervosa with the expected frequencies as computed using the census data shown in parentheses.
Frequencies: Observed (Expected)
Region
West South Midwest Northeast
58 (43.1) 19 (23.0) 22 (27.2) 22 (27.7)
To describe the details of the significant result, compare the provided observed and expected frequencies.
Which of the following statements best describes the results?
a. A greater proportion of the adolescent girls with anorexia nervosa live in the Northeast than live in the other regions when compared to the general US population
b. A greater proportion of the adolescent girls with anorexia nervosa live in the West than live in the other regions when compared to the general US population
c. A greater proportion of the adolescent girls with anorexia nervosa live in the South than live in the other regions when compared to the general US population