# HW6 Solns - Assignment 6 Solutions x 11.32 State How large...

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Assignment 6 Solutions 11.32. State: How large an SRS is needed to reduce the standard deviation of x to 0.5 inch? Formulate: Use the formula for the standard deviation of the mean, and solve for the sample size. Solve: We need to choose n so that 2.8 / n = 0.5. That means n = 5.6, so n = 31.36. Because n must be a whole number, take n = 32. Conclude: A sample of size 32 will give a standard deviation (slightly below) 0.5 inch.

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14.10. n = 2.576  15 5 2 = . 59.72 —take n = 60. 15.6. H 0 : μ = 20 min; H a : μ ≠ 20 min. 15.19. State: Do student SATM scores improve on their second attempt? Formulate: Let μ be the mean change in SATM score. We test H 0 : μ = 0 versus H a : μ > 0; the alternative is one-sided because we expect scores to increase. Solve: We were told the 46 students were “randomly” chosen, and that we “know” that changes in score follow a Normal distribution with standard deviation 50 points. We find that x = 13.1087 points, so the test statistic is
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HW6 Solns - Assignment 6 Solutions x 11.32 State How large...

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