please explain. Waht are all the SD formule one needs to remmeber.
thanx in advance !
If a sample data has mean = 20 and std deviation=3.0 , which of the following is more than 2.5 std deviation from mean.
12,13.5,17,23.5,26.5
GMATPrep test 1 SD problem
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Hey there,
This is very easy one. All you have to do is just ad/subtract SD to/from the mean. Before you have to multiply by the given number, which is 2.5 SD. Thus,
20 + (2.5 * 3) = 20 + 7.5 = 27.5
20 - (2.5 * 3) = 20 - 7.5 = 12.5.
Your data should be outside the range of 12.5 ~ 27.5. All the numbers lie in the range except 12, the answer must be [A].
This is very easy one. All you have to do is just ad/subtract SD to/from the mean. Before you have to multiply by the given number, which is 2.5 SD. Thus,
20 + (2.5 * 3) = 20 + 7.5 = 27.5
20 - (2.5 * 3) = 20 - 7.5 = 12.5.
Your data should be outside the range of 12.5 ~ 27.5. All the numbers lie in the range except 12, the answer must be [A].
Last edited by smushkas on Tue Jan 29, 2008 2:14 pm, edited 1 time in total.
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Smushka's explanation is 100% correct, I just want to add a strategic guessing tip for this question.rainbownlife wrote:please explain. Waht are all the SD formule one needs to remmeber.
thanx in advance !
If a sample data has mean = 20 and std deviation=3.0 , which of the following is more than 2.5 std deviation from mean.
12,13.5,17,23.5,26.5
Since the question is asking us for the number outside of 2.5 SD, the only possible choices are the two extremes, (a) and (e) - so, even if you're stuck, you have a 50/50 shot at the question.
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