If the arithmetic mean of 5 numbers is 20, and the arithmetic mean of another 3 numbers is 28, the combined mean of all 8 numbers is: MCQ with Answer and Explanation

Question

If the arithmetic mean of 5 numbers is 20, and the arithmetic mean of another 3 numbers is 28, the combined mean of all 8 numbers is:

A. 25

B. 22

C. 23

D. 24

Answer: Option C

Solution (By JKSSB Mock Tests)

Combined mean = (5×20 + 3×28) / (5+3) = (100 + 84) / 8 = 184 / 8 = 23. This formula weights each group's mean by its size.

This question belongs to: Accountancy and Statistics Statistics

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Question #1

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If each value in a dataset is increased by 10, which of the following measures remains unchanged?

A. First quartile

B. Range

C. Mean

D. Median

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Correct Answer: Option B

Explanation:
Range depends on difference between max and min; both increase by 10, so range unchanged.

This question belongs to: Accountancy and Statistics Statistics

Question #2

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If the crude death rate of population A is higher than B, but after age-standardization A's rate is lower, this indicates:

A. A has an older age structure

B. A has a younger age structure

C. Standardization is wrong

D. B has a higher mortality at every age

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Correct Answer: Option A

Explanation:
When an older population produces a higher crude rate despite lower age-specific rates, it is due to age confounding.

This question belongs to: Accountancy and Statistics Statistics

Question #3

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Which average is most appropriate for averaging ratios and rates when the denominators are variable?

A. Harmonic mean

B. Median

C. Arithmetic mean

D. Weighted arithmetic mean

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Correct Answer: Option D

Explanation:
When denominators vary, a weighted mean using denominators as weights is appropriate.

This question belongs to: Accountancy and Statistics Statistics

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