Chapter 12 ECON 261.docx

# Chapter 12 ECON 261.docx - Chapter 12ECON 261 Question 1...

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Chapter 12ECON 261 Question 1. What is the sample space for the random process “toss a die”? A. S = {1, 2, 3, 4, 5, 6} B. S = {odd or even} C. S = {0,1, 2, 3, 4, 5, 6} Feedback Correct. While the results might be classed as odd or even, the real possible outcomes are 1 through 6. It is not possible to have 0 spots show when you toss a die. Points awarded: 1 out of 1 Question 2. What might be a reasonable sample space for how much money is spent on a typical weekend date at your school? Note that this involves too many possible outcomes to list, so the sample space is given as an interval. A. S = [-10, 200] B. S = [10, 50] C. S = [0, 1000] D. S = [0, 25] Feedback Correct. The sample space must include all possible outcomes. It’s possible that a date could cost no money (a free campus event, for example). Also, having relatively small upper ends precludes the possibility of nice dinners out, for example. It’s impossible for a typical date to cost negative money. Points awarded: 1 out of 1 Question 3. If flipping a coin three times, the event “one head” consists of what outcomes? A . {one head and two tails} B. {HTT, THT, TTH} C. 3/8 D . {HTT} Feedback Correct. The elementary outcomes are all possible combinations of H and T for three tosses. There are eight total possible outcomes in the sample space. Points awarded: 1 out of 1 Question 4. If you are tossing three dice, A = {2, 3, 4, 5, 6} is an event in that sample space. A. True

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B. False Feedback Correct. When tossing three dice, the smallest possible result is 3 (1, 1, 1). Because 2 is not in S , this is not an event. Points awarded: 1 out of 1 Question 5. When drawing a card from a well-shuffled deck, all fifty-two cards are equally likely. What is the probability of drawing an ace? Enter the answer as a decimal rounded to three places. 0.077 Feedback Incorrect. There are four aces in a deck of fifty-two cards. 4/52 = 0.0769, which rounds to 0.077. Points awarded: 0 out of 1 Question 1. Consider the variable Joe’s weight next Friday. Is this discrete? A. Yes, because he only has one particular weight that day. B. No, because weights are usually rounded numbers. Feedback Correct. Variables like height and weight are not discrete. People typically round their actual weight (which can be measured in pounds, ounces, and fractions of ounces – whatever the accuracy of your scale is) to the nearest 5 or 10 pounds. Points awarded: 1 out of 1 Question 2. Consider the number of stars visible at 10 pm next Friday night. Is that a discrete variable? A. No, because there are too many possible values. B. Yes, because each star is seen or not. Feedback Correct. The number of stars visible at 10 pm next Friday is discrete. No one knows how many total stars there are (the astronomer Carl Sagan used to talk about “billions upon billions”) but each number from 0 (it’s totally cloudy and none are visible) to those billions is possible and could (if we wanted to) have a probability attached to it.
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