Answers to the MCO302 Fall07 midterm

# Answers to the - Answers to the MCO302 midterm 1"A properly conducted survey of local voters with a sampling error margin of 6 percentage points

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Answers to the MCO302 midterm 1. “A properly conducted survey of local voters, with a sampling error margin of 6 percentage points, found that 43 percent of respondents support Smith. If every voter was surveyed, we can be 95% certain we’d find that Smith’s actual support was in what range?” The error margin tells us that in 95% of samples gathered from a population, the results we would get from surveying everyone will fall within a certain number of percentage points around the result from the sample. (The other 5% of samples would fall outside the range, but probably not very far.) In this case, the error margin is plus or minus 6 points. So subtract 6 from 43 and add 6 to 43, and you get a range of 37% to 49%. Some of you confused sampling error margin with standard deviation. You saw the 95% confidence interval, figured that meant two S.D.s, and so doubled the 6% error margin to 12% 2. In a certain ASU classroom, the weight of men is an average of 178 pounds, with a standard deviation of 40 pounds. Assuming a normal distribution, approximately what percent of men in the class weigh between 138 and 218 pounds? The range of 138 to 218 pounds is 1 standard deviation on either side of the mean. The Empirical Rule says that 68% of values in a normal distribution will be within one standard deviation of the mean. Therefore, about 68% of the men in this class will weigh between 138 and 218. 3. In a certain ASU classroom, the weight of men is an average of 178 pounds, with a standard deviation of 40 pounds. What is the z-score of a male student who weighs 198? A z-score is simply the number of standard deviations that a particular value is above or below the mean. In this case, a student who weighs 198 pounds is 20 pounds above the mean. Twenty pounds is half of a standard deviation of 40 pounds. Therefore the z-score is 20/40, or a z-score of 0.5. It’s positive because it’s above the mean. 4. “What kind of variable is gender?” Gender is a CATEGORICAL variable. 5. Suppose that among a group of men the regression formula for the relationship between their height and weight was WEIGHT = HEIGHT * 5.9 - 227. Which of these would be the predicted weight for a man who is 70 inches tall? The formula would be WEIGHT = (70 * 5.9) - 227, or 186 pounds.

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6. “Madonna’s Miami mansion is much more expensive than nearby homes. Which one of these measures of central tendency is most appropriate to describe the typical home value in that neighborhood?” The correct answer is the MEDIAN value. The mean or average value would be dragged upward by having one multi-million dollar mansion counted along with the modest homes nearby. The mode is just the most common value, which may not be anywhere near the center of the data, as is the case with baseball salaries where the minimum salary
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## This note was uploaded on 05/05/2008 for the course MCO 302 taught by Professor Doig during the Fall '07 term at ASU.

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Answers to the - Answers to the MCO302 midterm 1"A properly conducted survey of local voters with a sampling error margin of 6 percentage points

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