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14 Sep 2020, 08:08
Kudos
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
50% (01:13) correct
50%
(01:13)
wrong
based on 124
sessions
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An art gallery has a number of paintings, each of which may include one or more depiction of trees. Is the standard deviation of the number of trees depicted in each painting equal to zero?
(1) At least one painting includes no depiction of trees.
(2) At least one painting includes a depiction of trees.
(1) At least one painting includes no depiction of trees.
(2) At least one painting includes a depiction of trees.
15 Sep 2020, 06:34
Kudos
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The wording is a bit strange (what is the source?), but the standard deviation of a collection of numbers is only zero if all the numbers are the same. In any other case, the standard deviation will be positive. We have no way to tell, using either Statement alone, if every painting depicts the same number of trees, but using both Statements, we know one painting has 0 trees, and one painting depicts some trees, so we know the numbers of trees are not all the same, and the standard deviation is thus not zero. So using both Statements, we know the answer to the question must be 'no', and the answer is C.
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