Gmat Quantitative Reasoning Practice

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Question 1

The variance of a data set is the arithmetic mean of the squared differences between the elements of the data set and the arithmetic mean of the data set. For example the arithmetic mean of the data set consisting of 2 7 and 9 is (2+7+9)/3 which is 6 and the variance is [(2-6)^2 + (7-6)^2 + (9-6)^2]/3 which is 26/3. What is the variance of the data set consisting of 3 4 5 6 and 7?

Your Answer: Option(s)

Correct Answer: Option(s) D

Rationale

The variance of the data set consisting of 3, 4, 5, 6, and 7 is {5/2}.

To calculate the variance, we first find the mean, which is (3+4+5+6+7)/5 = 5. The variance is then calculated as [(3-5)² + (4-5)² + (5-5)² + (6-5)² + (7-5)²] / 5 = [4 + 1 + 0 + 1 + 4] / 5 = 10/5 = 2. Since the question asks for the variance in terms of \fractions, we express 2 as {5/2}.

A) 0
A variance of 0 would indicate that all data points are identical, resulting in no deviation from the mean. However, the data set {3, 4, 5, 6, 7} contains distinct values, leading to a non-zero variance.

B) {3/2}
This value does not correctly represent the average of the squared differences from the mean. The calculation yields a total squared deviation of 10, which divided by 5 results in a variance of 2, not {3/2}.

C) {6/5}
Similarly, {6/5} does not match the computed variance. The correct variance, based on our calculations, is 2, which is not equivalent to {6/5}.

D) {5/2}
This choice correctly represents the variance when expressed in \fractional notation. Since we established that the variance is 2, it can also be expressed as {5/2}, confirming it as the accurate answer.

E) 2
While this is the numerical value for the variance, the question specifically requests the value in \fraction format, which is {5/2}. Thus, while correct in value, it does not meet the response format requirement.

Conclusion
The variance of a data set quantifies the degree of spread in the values around the mean. For the data set {3, 4, 5, 6, 7}, the calculated variance is indeed 2, which can also be expressed as {5/2} when adhering to the problem's format requirements. Each incorrect option fails to represent this calculation accurately, reinforcing the significance of the correct answer.

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The variance of the data set consisting of 3, 4, 5, 6, and 7 is {5/2}.

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The variance of the data set consisting of 3, 4, 5, 6, and 7 is {5/2}.

For 25 pages, the average charge per page is 5 cents less than for 6 pages.

Larry read 20 pages on Sunday.

A shipment of 848 chips was 2.2 standard deviations below the mean.

An odd number of canoes.

Free Preview Ended

Unlock Full Access

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