(c) Find the probability that Xtakes a value within 1 standard deviation of its mean.

© 2011 BFW Publishers The Practice of Statistics, 4/e- Chapter 6 275 Test 6A AP Statistics Name: Part 1: Multiple Choice.Circle the letter corresponding to the best answer.1. A marketing survey compiled data on the number of personal computers in households. If X= the number of computers in a randomly-selected household, and we omit the rare cases of more than 5 computers, then Xhas the following distribution: What is the probability that a randomly chosen household has at least two personal computers? (a) 0.19 (b) 0.20 (c) 0.29 (d) 0.39 (e) 0.61 2. A random variable Xhas a probability distribution as follows: Where k is a positive constant. The probability P(X< 2.0) is equal to 3. A business evaluates a proposed venture as follows. It stands to make a profit of $10,000 with probability 3/20, to make a profit of $5000 with probability 9/20, to break even with probability 5/20, and to lose $5000 with probability 3/20. The expected profit in dollars is 4.Roll one 8-sided die 10 times. The probability of getting exactly 3 sevens in those 10 rolls is given by 351017388§·§·§·¨¸ ¨¸¨¸©¹©¹©¹371017388§·§·§·¨¸ ¨¸¨¸©¹©¹©¹35817388§·§·§·¨¸ ¨¸¨¸©¹©¹©¹37817388§·§·§·¨¸ ¨¸¨¸©¹©¹©¹371071388§·§·§·¨¸ ¨¸¨¸©¹©¹©¹X 0 1 2 3 4 5 P(X) 0.240.370.200.110.050.03X 0 1 2 3 P(X) 2k 3k 13k2k

276 The Practice of Statistics, 4/e- Chapter 6 © 2011 BFW Publishers 5. X and Y are independent random variables, and aand bare constants. Which one of the following statements is true?(a) XYXYVVV´´(b) ±²±²±²VarVarVarXYXYµ´(c) ±²±²VarVarabXbX´(d) XYXYVVVµµ(e) ±²±²±²22VarVarVarXYXY´´6. Let the random variable Xrepresent the profit made on a randomly selected day by a certain store. Assume that Xis Normal with mean $360 and standard deviation $50. What is P(X> $400)? 7.A dealer in the Sands Casino in Las Vegas selects 40 cards from a standard deck of 52 cards. Let Ybe the number of red cards (hearts or diamonds) in the 40 cards selected. Which of the following best describes this setting?

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