In: Statistics and Probability
The data below shows the sugar content in grams of several brands of children's and adults' cereals. Create and interpret a 95% confidence interval for the difference in the mean sugar content,
mu Subscript Upper C Baseline minus mu Subscript Upper AμC−μA.
Be sure to check the necessary assumptions and conditions. (Note: Do not assume that the variances of the two data sets are equal.)
| Full data set
 
  | 
| Children's cereal:
 40.6 comma40.6, 58.3 comma58.3, 47 comma47, 42.6 comma42.6, 52.2 comma52.2, 47 comma47, 53.3 comma53.3, 41.7 comma41.7, 44.9 comma44.9, 43 comma43, 47.9 comma47.9, 40.2 comma40.2, 35.6 comma35.6, 56.4 comma56.4, 48.5 comma48.5, 54.3 comma54.3, 36.9 comma36.9, 56.4 comma56.4, 44.7 comma44.7, 34.834.8 | 
| Adults' cereal:
 21.8 comma21.8, 26.1 comma26.1, 1.8 comma1.8, 7.4 comma7.4, 3.1 comma3.1, 24.3 comma24.3, 16.6 comma16.6, 12.3 comma12.3, 24.8 comma24.8, 9.3 comma9.3, 6.9 comma6.9, 10.6 comma10.6, 15.9 comma15.9, 11.5 comma11.5, 1.8 comma1.8, 18.8 comma18.8, 1.6 comma1.6, 2.3 comma2.3, 2.6 comma2.6, 9.3 comma9.3, 11.1 comma11.1, 1.7 comma1.7, 2.9 comma2.9, 3.6 comma3.6, 6.8 comma6.8, 2.7 comma2.7, 17.1 comma17.1, 7.9 comma7.9, 17.5 comma17.5, 13.9 | 
The 95% confidence interval for the difference in the mean sugar content,μC−μA, is between 32.0585 and 40.6292.
We are 95% confident that the true mean difference in the mean sugar content,μC−μA, is between 32.0585 and 40.6292.
| Children's cereal | Adults' cereal | |
| 40.6 | 21.8 | |
| 58.3 | 26.1 | |
| 47 | 1.8 | |
| 42.6 | 7.4 | |
| 52.2 | 3.1 | |
| 47 | 24.3 | |
| 53.3 | 16.6 | |
| 41.7 | 12.3 | |
| 44.9 | 24.8 | |
| 43 | 9.3 | |
| 47.9 | 6.9 | |
| 40.2 | 10.6 | |
| 35.6 | 15.9 | |
| 56.4 | 11.5 | |
| 48.5 | 1.8 | |
| 54.3 | 18.8 | |
| 56.4 | 1.6 | |
| 44.7 | 2.3 | |
| 34.8 | 2.6 | |
| 9.3 | ||
| 11.1 | ||
| 1.7 | ||
| 2.9 | ||
| 3.6 | ||
| 6.8 | ||
| 2.7 | ||
| 17.1 | ||
| 7.9 | ||
| 17.5 | ||
| 13.9 | ||
| Children's cereal | Adults' cereal | |
| 46.811 | 10.467 | mean | 
| 6.936 | 7.689 | std. dev. | 
| 19 | 30 | n | 
| 41 | df | |
| 36.3439 | difference (Children's cereal - Adults' cereal) | |
| 2.1220 | standard error of difference | |
| 32.0585 | confidence interval 95.% lower | |
| 40.6292 | confidence interval 95.% upper | |
| 4.2854 | margin of error | 
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