spellman.2008.Exam3KEYa

spellman.2008.Exam3KEYa - Page 1 PSYC305EXAM3.1b Spring2008...

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Page 1 PSYC 305 – EXAM 3.1b Name:__________KEY__________ Spring 2008 PROFESSOR SPELLMAN e-mail ID:_____________________ You are allowed to bring ONE sheet of paper (with writing on both sides) into the exam. You may use a calculator. The total for the exam is 100 points. There is a z table at the back that you can rip off and also use as scratch paper. When you are using z-scores, just compute to TWO decimal places. Curvy Questions (5) 1. Which of the following are true about the normal curve? Circle all that apply: ONLY A is CORRECT. D is confusing and so both answers are scored correct. a. The mean, median, and mode MUST be equal. b. The ends of the curve (on both sides) touch the y-axis at between 3 and 4 standard deviations from the mean. c. The distribution must be taller than it is wide. d. About 34% of scores are within one standard deviation of the mean. e. The shape can be either positively or negatively skewed. (12) 2. Suppose people's scores on a morality scale are normally distributed with a mean of 50 and standard deviation of 10. Use the normal curve table for the problems below. Be sure to show your work. IN ALL OF THE BELOW – HARD TO GET PARTIAL CREDIT – you should have an estimate of how big the answer should be. Missing a step – like not subtracting from .50 – is not just an arithmetic error -- that is a conceptual error. a. If you picked a person at random, what is the probability that she has a score higher than 72 on this scale? 4 points – z = 72-50/10 = 2.2 z to mean is .486 .50-.486 = .014 or 1.4% rounding okay b. What score would a person need to be in the top 5% of this distribution, the most moral? 4 points top 5 % = 1.64 (or can use 1.65) X = (z * SD) + M so = (1.64 * 10) + 50 = 66.4% c. Suppose John took this test and got a 55 and Bill, his friend, got a 35. What percentage of people would get a score between John and Bill? (4) 4 points John z = 55-50 / 10 = .5 z to mean is .191 (might say above .691) Bill z = 35 – 50 / 10 = -1.5 z to mean is .433 (and he is above only .067) So, bill is .43 below and John is . 19 above – therefore there is 62.4% between them. OR .691 - .067 = .62 or 62% between them. No credit for using “shortcuts” that don’t work or for doing .43-.19 to get .24.
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Page 2 3. PROJECT : Two students from the Comm School (the UVA undergraduate business school) had to do project in which they came up with a business plan for a new business to open in Charlottesville. One of their first steps was to survey people in Charlottesville to determine whether their new business might succeed here. They were thinking about opening a bar/nightclub that had “exotic dancers” and private rooms for “private services” upstairs. (If you don’t know what this implies, please ask someone giving this exam.) The survey included questions like: How often do you go to a bar to drink? Have you ever paid money for intimate companionship?
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This note was uploaded on 09/25/2008 for the course PSYCH 305 taught by Professor Freeman during the Fall '08 term at UVA.

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spellman.2008.Exam3KEYa - Page 1 PSYC305EXAM3.1b Spring2008...

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