1 / 6

CONFIDENCE INTERVAL FOR 2-SAMPLE MEANS

CONFIDENCE INTERVAL FOR 2-SAMPLE MEANS. Case 1: calcium and blood pressure.

efrem
Download Presentation

CONFIDENCE INTERVAL FOR 2-SAMPLE MEANS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CONFIDENCE INTERVAL FOR 2-SAMPLE MEANS

  2. Case 1: calcium and blood pressure Does increasing the amount of calcium in our diet reduce blood pressure? Examination of a large sample of people revealed a relationship between calcium intake and blood pressure. The relationship was strongest for black men. Such observational studies do not establish causation. Researchers therefore designed a randomized comparative experiment. The subjects in part of the experiment were 21 healthy black men. A randomly chosen group of 10 of the men received a calcium supplement for 12 weeks. The control group of 11 men received a placebo pill that looked identical. The experiment was double-blind. The response variable is the decrease in systolic (top number) blood pressure for a subject after 12 weeks, in millimeters of mercury. An increase appears as a negative response.

  3. From the data, calculate the summary statistics: and for the 11 men in Group 2 (placebo), Take Group 1 to be the calcium group and Group 2 the placebo group. Here are the data for the 10 men in Group 1 (calcium),

  4. Confidence interval For a 90% confidence interval, Table C shows that the t(9) critical value is t* = 1.833. We are 90% confident that the mean advantage of calcium over a placebo, μ1 = μ2, lies in the interval

  5. Warm-up Teaching reading, I An educator believes that new reading activities in the classroom will help elementary school pupils improve their reading ability. She arranges for a third-grade class of 21 students to follow these activities for an 8-week period. A control classroom of 23 third-graders follows the same curriculum without the activities. At the end of the 8 weeks, all students are given the Degree of Reading Power (DRP) test, which measures the aspects of reading ability that the treatment is designed to improve. Here are the data: (a) Is there good evidence that the new activities improve the mean DRP score? Carry out a test and report your conclusions. (b) Construct and interpret a 95% confidence interval for the difference in mean DRP scores.

  6. Answers: (a)H0: μt = μc vs. Ha: μt > μc. t = 2.311, 0.01 < P–value < 0.02 with df = 20 (TI calculator gives P–value = 0.0132 with df = 37.86). (b) (0.97, 18.94) with df = 20; (1.233, 18.68) on TI calculator with df = 37.86. With 95% confidence, we estimate the mean improvement in reading ability using the new reading activities compared to not using them over an 8–week period to be between 1.23 and 18.68 points.

More Related