112_review_midterm_answers2_s08

112_review_midterm_answers2_s08 - Given the above data •...

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Question 3: Given the following information, what is the best answer: 25 th percentile = 10 50 th percentile = 20 75 th percentile = 60 a) The plot is positively skewed and the best measure of scatter is 40 b) The plot is positively skewed and the best measure of scatter is 50 Right answer c) The plot is negatively skewed and the best measure of scatter is 40 d) The plot is negatively skewed and the best measure of scatter is 50 Question 19: In the general population IQ scores follow the normal distribution with mean = 100 and SD = 15 In a particular school district they think that their students are gifted (higher IQ than the general population). To test this hypothesis, they select a random sample of 225 students and administer an IQ test to them. They find the mean IQ for this sample to be 110.
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Unformatted text preview: Given the above data: • State the null and the alternative hypothesis in symbols and words. • Calculate the 95% confidence interval and decide whether based on this interval you reject or fail to reject the null. • Interpret the confidence interval. H0: μ = 100 Ha: > 100 95% CI = X +/- 1.96 * S ( X ) S ( X ) = S / N = 15/ 15 = 1 (the 15 in the denominator is the square root of 225) 95% CI = 110 +/- 1.96 * 1 = (108, 112) Since the 95% CI does not include the value of the population mean or = 100, we reject the null and conclude that the students in this district are more intelligent than the general population. We are 95% sure that their IQ scores fall between 108 to 112....
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