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Unformatted text preview: Practice Exam 2 (SummerA 2007) 1. Below is the Normal Probability plot for survival times of guineapigs: 600 500 400 300 200 100-100-200 99 95 90 80 70 60 50 40 30 20 10 5 1 Data Percent 7.603 AD* Goodness of Fit Normal Probability Plot for C1 ML Estimates - 95% CI Mean StDev 141.847 108.448 ML Estimates What is the shape of the distribution of lifetimes of guineapigs? a. Bell-shaped b. Skewed c. Bell-shaped but the data is granular d. None of the above 2. Suppose the heights of a simple random sample of 100 male sophomores were measured rather than 400. Which of the following statements is true? a) The margin of error for the 95% confidence interval would increase. b) The margin of error for the 95% confidence interval would decrease. c) The margin of error for the 95% confidence interval would stay the same, because the level of confidence has not changed. d) The standard deviation would decrease. 3. A simple random sample of five female basketball players is selected. Their heights (in cm) are 170, 175, 169, 183, and 177. What is the standard error of the mean of these height measurements? A) 2.538 B) 2.837 C) 5.075 D) 5.675 4. A 95% confidence interval (using the conservative value for the degrees of freedom) for 1 2 , based on two independent samples of sizes 18 and 20, respectively, gives us (45.6, 56.7). What was the observed difference between the two sample means 1 x and 2 x ? a. 11.1 b. 45.6 c. 51.15 d. 56.7 5. Central Middle School has calculated a 95% confidence interval for the mean height ( ) of 11-year old boys at their school and found it to be 56 2 inches. Which one of the following is true? A) There is a 95% probability that is between 54 and 58. B) There is a 95% probability that the true mean is 56, and there is a 95% chance that the true margin of error is 2. C) If we took many additional random samples of the same size and from each computed a 95% confidence interval for , approximately 95% of these intervals would contain . D) If we took many additional random samples of the same size and from each computed a 95% confidence interval for , approximately 95% of the time would fall between 54 and 58. 6. Suppose that the population of the scores of all high school seniors who took the SAT math (SATM) test this year follows a normal distribution with standard deviation = 100. You read a report that says, On the basis of a simple random sample of 100 high school seniors that took the SATM test this year, a confidence interval for...
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