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Confidence Intervals for the Mean

Difference between Means

Questions

Question 1 out of 4.

Select all of the assumptions that you need to make when creating a confidence interval on the difference between means.

  1. At least 2% of the population sampled
  2. Independently sampled values
  3. Homogeneity of variance
  4. Normally distributed populations
Question 2 out of 4.

You are comparing men and women on hours spent watching TV. You pick a sample of 12 men and 14 women and calculate a confidence interval on the difference between means. How many degrees of freedom does your t value have?

Question 3 out of 4.

You are comparing freshmen and seniors at your college on hours spent studying per day. You pick a sample of 11 people from each group. For freshmen, the mean was 3 and the variance was 1.2. For seniors, the mean was 2 and the variance was 1. Calculate a 90% confidence interval on the difference between means (freshmen - seniors). What is the lower limit of this CI?

Question 4 out of 4.

Scores on a test taken by 1st graders and 2nd graders were compared to look at development. The five 1st graders sampled got the following scores: 4, 3, 5, 7, 4. The five 2nd graders sampled got the following scores: 7, 9, 8, 6, 9. Compute the 95% confidence interval for the difference between means (2nd graders - 1st graders). You may use the Analysis Lab. What is the upper limit?

Grade	Score
  1	  4
  1	  3
  1	  5
  1	  7
  1	  4
  2	  7
  2	  9
  2	  8
  2	  6
  2	  9
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