Regular consumption of presweetened cereals con- tributes to tooth decay, heart
ID: 3158085 • Letter: R
Question
Regular consumption of presweetened cereals con- tributes to tooth decay, heart disease, and other degen- erative diseases, according to studies conducted by Dr. W. H. Bowen of the National Institute of Health and Dr. J. Yudben, Professor of Nutrition and Dietetics at the University of London. In a random sample con- sisting of 20 similar single servings of Alpha-Bits, the average sugar content was 11.3 grams with a standard deviation of 2.45 grams. Assuming that the sugar con- tents are normally distributed, construct a 95% con- fidence interval for the mean sugar content for single servings of Alpha-Bits.
Explanation / Answer
95% confidence interval for the population mean is
Sample mean +/- z-score for 95% confidence*standard deviation/sqrt sample size
11.3 +/- 1.96*2.45/sqrt 20
11.3 +/- 1.07
lower limit is 11.3 - 1.07 = 10.23
upper limit is 11.3 + 1.07 = 12.37
The CI is from 10.23 to 12.37