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INTRODUCTION TO STATISTICS: CHAPTER 9 HOMEWORK (INFERRING POPULATION MEANS) QUESTIONS WITH CORRECT ANSWERS

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9.1 A study of all the students at a small college showed a mean age of 20.7 and a standard deviation of 1 years. a. Are these numbers statistics or parameters? Explain. b. Label both numbers w ... ith their appropriate symbol (such as x-bar, μ, s, or σ). Correct Answer a. The numbers are parameters because they are for all the students, not a sample. b. μ=20.7; σ=1 A survey of 100 random full-time students at a large university showed the mean number of semester units that students were enrolled in was 10.4 with a standard deviation of 2 units. a. Are these numbers statistics or parameters? Explain. b. Label both numbers with their appropriate symbol (such as x-bar, μ, s, or σ). Correct Answer a. The numbers are statistics because they are for a sample of students, not all students. b. x-bar=10.4; s = 2 The distribution of the scores on a certain exam is N(40,10), which means that the exam scores are Normally distributed with a mean of 40 and standard deviation of 10. a. Sketch the curve and label, on the x-axis, the position of the mean, the mean plus or minus one standard deviation, and the mean plus or minus two standard deviations, and the mean plus or minus three standard deviations. b. Find the probability that a randomly selected score will be greater than 50. Shade the region under the Normal curve whose area corresponds to this probability. Correct Answer a. graph: +10 standard deviations b. Using the Empirical Rule, the probability that a randomly selected score will be greater than 50 is about 16% (Graph: Right-shaded). The distribution of the scores on a certain exam is N(70,5), which means that the exam scores are Normally distributed with a mean of 70 and standard deviation of 5. a. Sketch the curve and label, on the x-axis, the position of the mean, the mean plus or minus one standard deviation, and the mean plus or minus two standard deviations, and the mean plus or minus three standard deviations. [Show More]

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