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what is the SD deviation of the Set (P) ?

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what is the SD deviation of the Set (P) ? [#permalink] New post   03 Jul 2022, 06:11
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what is the SD deviation of the set P{} with mean 1.8 ?

statement 1 :- When each element of the set is multiply by 4,The standard deviation of the set becomes 7.2

statement 2 :- When each element of the set P{} is multiplied by 3,the standard deviation becomes thrice its mean.
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Re: what is the SD deviation of the Set (P) ? [#permalink] New post   08 Jul 2022, 22:31
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(1) When each number is multiplied by 4, the standard deviation also gets multiplied by 4. So the standard deviation was 1.8 to start with.
Sufficient

(2) By the same reasoning as above, we see that now the SD is 5.4, and it was 1.8 to start with.
Sufficient

=> Option D
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Re: what is the SD deviation of the Set (P) ? [#permalink] New post   09 Jul 2022, 10:54
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Multiplication affects standard deviation by a scaling factor. If we multiply every data point by a constant K, then the standard deviation is multiplied by the same factor K. In fact, the mean is also scaled by the same factor K.

1)When each element of the set is multiply by 4,The standard deviation of the set becomes 7.2
SD becomes 7.2 on multiplying each member of set P by 4. So SD of P was 7.2/4 = 1.8. Sufficient.


2) When each element of the set P{} is multiplied by 3,the standard deviation becomes thrice its mean.

i.e SD was equal to mean as when multiplied by 3 times, SD became three times mean = 1.8*3 = 5.4. So, SD was 5.4/3 1.8. Sufficient.

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Re: what is the SD deviation of the Set (P) ? [#permalink]
09 Jul 2022, 10:54
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