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Unformatted text preview: Stat3011 Solutions to Sample Midterm 2 Solutions to Sample Midterm 2 Section 1: Multiple Choice 1. 40% of the students in a large introductory statistics course earn a grade of A for the course. Suppose you choose 10 students at random from the class. What is the probability that exactly 8 of these students earn a grade of A? (a) 0.000655 (b) 0.0049 (c) 0.0106 (d) 0.0123 NOTE: X ∼ Bin (10 ,. 4) 2. Which of the following statements is not true regarding the confidence interval for mean μ ? (a) The margin of error for a 95% confidence interval for mean μ decreases as sample size increases. (b) For a fixed sample size n , the margin of error for a confidence interval for mean μ increases as the confidence level decreases. (c) The margin of error for a 95% confidence interval for mean μ decreases as the sample standard deviation decreases. 3. Suppose we have a sample of size 9 from a population with mean μ = 5 and standard deviation σ = 1. Which of the following statements about the sampling distribution of x is true? (a) The sampling distribution has a mean of 5 and a standard deviation of 1. (b) x ∼ N (5 , 1 / 3) no matter what the distribution of the population looks like. (c) x ∼ N (5 , 1 / 3) if the data come from a population with a normal distribution. 4. In product testing at a bungee cord factory, researchers collect data to test H : μ = 200 versus H a : μ > 200 where μ is the mean lifetime of their ropes (in number of safe jumps). Suppose that, based on their data, the researchers conclude that the average bungee cord lifetime is not significantly longer than 200 jumps when it actually is . What type of error (if any) has occurred? (a) Type I error ⇐ A Type I error in this context could lead to terrible consequences (broken bones)! (b) Type II error (c) no error 1/7 Stat3011 Solutions to Sample Midterm 2 5. The manufacturer of a certain food product containing the fat substitute ‘Olean’ claims that only 15% of its customers experience negative side effects. Thinking that this claim is an underestimation of the true occurrence of side effects, you give the food product to a random sample of 72 people and observe their reactions. How should you proceed?...
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This note was uploaded on 10/02/2011 for the course STAT 3011 taught by Professor Wang,zhan during the Spring '09 term at Minnesota.
- Spring '09