Having done poorly on a particular exam in a junior high school, 24 students decide to write the exam again to try and improve their mark. Results are given in the following table Student Attempt 1 (A₁) Attempt 2 (A₂) Difference (d = A₁ - A₂) n 24 24 24 Average 52 56 -4.0 Standard deviation 3.8 4.4 3.0 (a) Find a 98% confidence interval for the difference in mean scores between attempt 1 and attempt 2. (Round your answers to 4 decimal places, if needed.) (b) Based on this confidence interval, can we conclude there is a difference in mean scores between attempt 1 and attempt 2? O Yes, since the interval contains 0. O No, since the interval contains 0. O Yes, since the interval is completely below 0. O No, since the interval is completely below 0.

2 different treatments were used to speed the relief time (in minutes) of migraines. 8 subjects received each treatment. The recovery times are listed below. Treatment 1: 20 19 29 25 34 32 39 38 Treatment 2: 18 18 16 17 29 28 21 37 Construct a 90% confidence interval for the difference in the relief time between the 2 treatments.

Question:

A. True or False? A researcher compares the BMI of two populations of individuals from different socioeconomic backgrounds and finds that the proportion of individuals considered obese and from a poor background is .37 (n = 112), and the proportion of individuals considered obese and from an affluent background is .27 (n = 87); a 95% confidence interval for the risk difference for obesity among members of the poor population compared to the affluent population is (-0.03, 0.23). B. Why is it true or false?

Suppose the mean height in inches of all 9th grade students at one high school is estimated. The population standard deviation is 4 inches. The heights of 9 randomly selected students are 72, 61, 65, 64, 61, 67, 71, 63 and 72. x¯ =? Margin of error at 90% confidence level =? 90% confidence interval = [__.__ , __.__]

Using traditional methods it takes 107 hours to receive an advanced flying license. A new training technique using Computer Aided Instruction (CAI) has been proposed. A researcher used the technique on 150 students and observed that they had a mean of 106 hours. Assume the population standard deviation is known to be 5 . Is there evidence at the 0.01 level that the technique performs differently than the traditional method? Step 1 of 6 : State the null and alternative hypotheses.