Chapter 5: Problem 19
When describing test results, someone objects to the conversion of raw scores into standard scores, claiming that this constitutes an arbitrary change in the value of the test score. How might you respond to this objection?
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Chapter 5: Problem 19
When describing test results, someone objects to the conversion of raw scores into standard scores, claiming that this constitutes an arbitrary change in the value of the test score. How might you respond to this objection?
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IQ scores on the WAIS test approximate a normal curve with a mean of 100 and a standard deviation of \(15 .\) What IQ score is identified with (a) the upper 2 percent, that is, 2 percent to the right (and 98 percent to the left)? (b) the lower 10 percent? (c) the upper 60 percent? (d) the middle 95 percent? [Remember, the middle 95 percent straddles the line perpendicular to the mean (or the 50th percentile), with half of 95 percent, or 47.5 percent, above this line and the remaining 47.5 percent below this line.] (e) the middle 99 percent?
Assume that the burning times of electric light bulbs approximate a normal curve with a mean of 1200 hours and a standard deviation of 120 hours. If a large number of new lights are installed at the same time (possibly along a newly opened freeway), at what time will (a) 1 percent fail? (Hint: This splits the total area into .0100 to the left and .9900 to the right.) (b) 50 percent fail? (c) 95 percent fail? (d) If a new inspection procedure eliminates the weakest 8 percent of all lights before they are marketed, the manufacturer can safely offer customers a money-back guarantee on all lights that fail before ______ hours of burning time.
Suppose that the burning times of electric light bulbs approximate a normal curve with a mean of 1200 hours and a standard deviation of 120 hours. What proportion of lights burn for (a) less than 960 hours? (b) more than 1500 hours? (c) within 50 hours of the mean? (d) between 1300 and 1400 hours?
Express each of the following scores as a z score: (a) Margaret's \(1 Q\) of \(135,\) given a mean of 100 and a standard deviation of 15 (b) a score of 470 on the SAT math test, given a mean of 500 and a standard deviation of 100 (c) a daily production of 2100 loaves of bread by a bakery, given a mean of 2180 and a standard deviation of 50 (d) Sam's height of 69 inches, given a mean of 69 and a standard deviation of 3 (e) a thermometer-reading error of -3 degrees, given a mean of 0 degrees and a standard deviation of 2 degrees
Convert each of the following test scores to \(z\) scores: $$\begin{array}{|lccc|} \hline & \text { TEST SCORE } & \text { MEAN } & \text { STANDARD DEVIATION } \\\ \text { (a) } & 53 & 50 & 9 \\ \text { (b) } & 38 & 40 & 10 \\ \text { (c) } & 45 & 30 & 20 \\\\\text { (d) } & 28 & 20 & 20 \\\\\hline\end{array}$$
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