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The table shows the number of calls received by each of five operators

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The table shows the number of calls received by each of five operators  [#permalink]

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New post 11 Oct 2019, 02:37
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The table shows the number of calls received by each of five operators during each of 4 one-hour periods. For which operator was the standard deviation of the numbers of calls received during these 4 periods the least?

A. Operator A
B. Operator B
C. Operator C
D. Operator D
E. Operator E

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Re: The table shows the number of calls received by each of five operators  [#permalink]

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New post 11 Oct 2019, 02:56
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Bunuel wrote:
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GMAT_PS_PREP_T2_39.png

The table shows the number of calls received by each of five operators during each of 4 one-hour periods. For which operator was the standard deviation of the numbers of calls received during these 4 periods the least?

A. Operator A
B. Operator B
C. Operator C
D. Operator D
E. Operator E


Operator A --> 3, 7, 7, 3: Mean = 5
Operator B --> 4, 5, 5, 6: Mean = 5
Operator C --> 8, 2, 5, 5: Mean = 5
Operator D --> 6, 4, 4, 6: Mean = 5
Operator E --> 3, 4, 5, 6: Mean = 5

Deviations from Mean:
Operator A --> 3-5, 7-5, 7-5, 3-5 --> -2, 2, 2, -2
Operator B --> 4-5, 5-5, 5-5, 6-5 --> -1, 0, 0, 1
Operator C --> 8-5, 2-5, 5-5, 5-5 --> 3, -3, 0, 0
Operator D --> 6-5, 4-5, 4-5, 6-5 --> 1, -1, -1, 1
Operator E --> 3-5, 4-5, 5-5, 6-5 --> -2, -1, 0, 1

We can clearly see Operator B is least deviated from Mean value

IMO Option B
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Re: The table shows the number of calls received by each of five operators  [#permalink]

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New post 11 Oct 2019, 07:42
Bunuel wrote:
Attachment:
GMAT_PS_PREP_T2_39.png

The table shows the number of calls received by each of five operators during each of 4 one-hour periods. For which operator was the standard deviation of the numbers of calls received during these 4 periods the least?

A. Operator A
B. Operator B
C. Operator C
D. Operator D
E. Operator E


mean value for each operator is 5
and the least variation along mean is observed for operator B ;
IMO B
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Re: The table shows the number of calls received by each of five operators  [#permalink]

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New post 12 Oct 2019, 16:15
Bunuel wrote:
Attachment:
GMAT_PS_PREP_T2_39.png

The table shows the number of calls received by each of five operators during each of 4 one-hour periods. For which operator was the standard deviation of the numbers of calls received during these 4 periods the least?

A. Operator A
B. Operator B
C. Operator C
D. Operator D
E. Operator E


We notice that the sum for each operator is 20; therefore, the mean number of calls for each operator is 5.

Since the standard deviation is a measure of how far data points are from the mean, we should look for the row with the values closest to 5.

Operator B has two calls equal to the mean, and two other calls that are pretty close to the mean. All the other operators either have no calls equal to the mean, or have other calls that are far away from the mean (or both). Thus, Operator B has the smallest standard deviation.

Answer: B
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Re: The table shows the number of calls received by each of five operators   [#permalink] 12 Oct 2019, 16:15
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