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Math Help - simple stats questions #2

  1. #1
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    simple stats questions #2

    hey everyone!! have a few questions that are for an economics subject but are basic stats stuff, and ive done them i just wanted someone to check if i have the right/wrong answer and help me if i have the wrong answer? thanks in advance!!

    QUESTION FOUR
    Baby Pty Ltd. is planning to launch a new brand of makeup product. Based on market research, if sales are high they can make a profit of $24.9 million per year. If sales are 'so so' they can make a profit of $5.5 million per year. Finally, if sales are low they can lose $2.5 million. The probabilities for the two profit scenarios are 0.47 and 0.29, respectively. Calculate the variance for the product (in $ millions sqd) to two decimal places.
    i got = 140.44

    QUESTION FIVE
    A laser printer in a large firm operates properly 32% of the time. A random sample of five jobs is taken. What is the probability that the printer operates properly more than three times? (3 dec pl)
    i got = 0.039

    QUESTION SIX
    A total of 203 shoppers at a large suburban mall were asked two questions:
    1. Did you see a TV ad for the sale at store M?
    2. Did you shop at store M?
    93 shoppers indicated they had seen the advertisement; 67 had seen the ad and did not shop at M; 88 shoppers had not shopped at M. One of the shoppers is chosen at random. What is the probability that the person saw the ad and shopped at M? (2 dec pl)
    i got = 0.13

    thanks so much!!!
    Last edited by mr fantastic; September 3rd 2009 at 05:57 AM. Reason: Moved questions to new thread
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  2. #2
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    Quote Originally Posted by wik_chick88 View Post
    hey everyone!! have a few questions that are for an economics subject but are basic stats stuff, and ive done them i just wanted someone to check if i have the right/wrong answer and help me if i have the wrong answer? thanks in advance!!

    QUESTION FOUR
    Baby Pty Ltd. is planning to launch a new brand of makeup product. Based on market research, if sales are high they can make a profit of $24.9 million per year. If sales are 'so so' they can make a profit of $5.5 million per year. Finally, if sales are low they can lose $2.5 million. The probabilities for the two profit scenarios are 0.47 and 0.29, respectively. Calculate the variance for the product (in $ millions sqd) to two decimal places.
    i got = 140.44

    QUESTION FIVE
    A laser printer in a large firm operates properly 32% of the time. A random sample of five jobs is taken. What is the probability that the printer operates properly more than three times? (3 dec pl)
    i got = 0.039

    QUESTION SIX
    A total of 203 shoppers at a large suburban mall were asked two questions:
    1. Did you see a TV ad for the sale at store M?
    2. Did you shop at store M?
    93 shoppers indicated they had seen the advertisement; 67 had seen the ad and did not shop at M; 88 shoppers had not shopped at M. One of the shoppers is chosen at random. What is the probability that the person saw the ad and shopped at M? (2 dec pl)
    i got = 0.13

    thanks so much!!!
    It's much easier to check answers if the working is included.


    I checked question 4 and got the same answer as you:

    Pr(X = 24.9) = 0.47, Pr(X = 5.5) = 0.29, Pr(X = -2.5) = 0.24.

    E(X) = 12.698, E(X^2) = 301.677.

    Var(X) = E(X^2) - (E(X))^2 = 140.44 (rounded to two decimal places).
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