If the sum of 50 observations is 500, the arithmetic mean is 10. If each observation is multiplied by 3, the new mean is: MCQ with Answer and Explanation

Question

If the sum of 50 observations is 500, the arithmetic mean is 10. If each observation is multiplied by 3, the new mean is:

A. 13

B. 300

C. 30

D. 10

Answer: Option C

Solution (By JKSSB Mock Tests)

Mean scales by the same factor.

This question belongs to: Accountancy and Statistics Statistics

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Question #1

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In a frequency distribution with exclusive class intervals 0-10, 10-20, 20-30, a value exactly equal to 20 should be included in:

A. Either 10-20 or 20-30

B. Excluded from both

C. 10-20

D. 20-30

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Correct Answer: Option D

Explanation:
In exclusive classification, the upper limit is excluded; thus 20 belongs to the class 20-30.

This question belongs to: Accountancy and Statistics Statistics

Question #2

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If the number of women aged 15-49 is 20,000 and live births are 500, GFR per 1000 women is:

A. 20

B. 40

C. 25

D. 50

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Correct Answer: Option C

Explanation:
GFR = (500 / 20000) × 1000 = 25 per 1000 women.

This question belongs to: Accountancy and Statistics Statistics

Question #3

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A medical test has 95% sensitivity and 90% specificity. If disease prevalence is 1%, the probability that a person with a positive test actually has the disease is approximately:

A. 95.0%

B. 50.0%

C. 15.3%

D. 8.7%

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Correct Answer: Option D

Explanation:
Using Bayes: P(Disease|Positive) = [Sensitivity × Prevalence] / [Sensitivity×Prev + (1-Specificity)×(1-Prev)] = (0.95×0.01) / (0.95×0.01 + 0.10×0.99) = 0.0095 / (0.0095 + 0.099) = 0.0095/0.1085 ≈ 0.0876 ≈ 8.7%. Highlights low positive predictive value when prevalence is low.

This question belongs to: Accountancy and Statistics Statistics

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