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resilient
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 Posted: Sun May 11, 2008 12:00 pm Post subject: sd |
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Set X consists of 8 integers. Is the standard deviation of set X equal to zero?
(1) The range of set X is equal to 3
(2) The mean of set X is equal to 5
qa is [/spoiler]a
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Stuart Kovinsky
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| Posted: Sun May 11, 2008 7:46 pm Post subject: Re: sd |
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| resilient wrote: | Set X consists of 8 integers. Is the standard deviation of set X equal to zero?
(1) The range of set X is equal to 3
(2) The mean of set X is equal to 5
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The only way a set can have a SD of 0 is if all the terms are the same.
(1) range is 3. Well, if range > 0, then some of the terms are different. Therefore, the set definitely does NOT have a SD of 0: sufficient.
(2) mean is 5. Set could be {5,5,5} (so YES, SD=0) or set could be {3,5,7} (so NO, SD not = 0): insufficient.
(1) is suff and (2) isn't: choose (A).
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resilient
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| Posted: Mon May 12, 2008 6:56 am Post subject: thanks |
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sweetness and genious
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