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Magazine Problem 7
Suppose your Statistics professor reports test grades as z-scores, and you got a score of \(2.20\) on an exam. Write a sentence explaining what that means.
Problem 10
People with \(z\) -scores above \(2.5\) on an IQ test are sometimes classified as geniuses. If IQ scores have a mean of 100 and a standard deviation of 16 points, what IQ score do you need to be considered a genius?
Problem 38
Based on the Normal model \(N(100,16)\) describing IQ scores, what percent of people's IQs would you expect to be a) over \(80 ?\) b) under \(90 ?\) c) between 112 and \(132 ?\)
Problem 39
Based on the model \(N(1152,84)\) describing Angus steer weights, what are the cutoff values for a) the highest \(10 \%\) of the weights? b) the lowest \(20 \%\) of the weights? c) the middle \(40 \%\) of the weights?
Problem 42
Consider the IQ model \(N(100,16)\) one last time. a) What IQ represents the 15 th percentile? b) What IQ represents the 98 th percentile? c) What's the IQR of the IQs?
