A researcher wishes to determine if vitamin E supplements could increase cognitive ability among elderly women. In 1999 the researcher recruits a sample of elderly women age 75-80. At the time of the enrollment into the study, the women were randomized to either take Vitamin E, or a placebo for six months. At the end of the six month period, the women were given a cognition test. Higher scores on this test indicate better cognition. The mean and standard deviation of the test scores of 81 women who took vitamin E supplements was 27 and 6.9 respectively. The mean and standard deviation of the test scores of the 90 women who took placebo supplements was 24 and 6.2, respectively.C Computea 95% confidence interval for the mean difference in cognition test scores between Vitamin E and placebo group.

A researcher wishes to determine if vitamin E supplements could increase cognitive ability among elderly women. In 1999 the researcher recruits a sample of elderly women age 75-80. At the time of the enrollment into the study, the women were randomized to either take Vitamin E, or a placebo for six months. At the end of the six month period, the women were given a cognition test. Higher scores on this test indicate better cognition. The mean and standard deviation of the test scores of 81 women who took vitamin E supplements was 27 and 6.9 respectively. The mean and standard deviation of the test scores of the 90 women who took placebo supplements was 24 and 6.2, respectively.C Computea 95% confidence interval for the mean difference in cognition test scores between Vitamin E and placebo group.