The combined mean of three groups with means 20, 30, 40 and sizes 10, 15, 25 is: MCQ with Answer and Explanation

The combined mean of three groups with means 20, 30, 40 and sizes 10, 15, 25 is:
A. 33
B. 35
C. 32
D. 30
Answer: Option A
Solution (By JKSSB Mock Tests)
Sum = 200+450+1000=1650, N=50, Mean=33.

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Practice More Statistics Questions

Question #1
In a 2×2 table, if (AB)=100, (Aβ)=150, (αB)=200, (αβ)=250, the total N is:
A. 900
B. 800
C. 700
D. 600

Correct Answer: Option C


Explanation:
N = sum of all ultimate class frequencies = 100 + 150 + 200 + 250 = 700. This is the total population classified by the two attributes.

This question belongs to: Accountancy and Statistics Statistics
Question #2
Assertion (A): For a moderately skewed distribution, mean – mode ≈ 3(mean – median). Reason (R): In any skewed distribution, the median always lies between the mean and mode. Choose the correct option:
A. Both A and R are true, and R is the correct explanation of A
B. A is false, R is true
C. A is true, R is false
D. Both A and R are true, but R is not the correct explanation of A

Correct Answer: Option D


Explanation:
The empirical relationship (A) is true for moderate skewness. In skewed distributions, median lies between mean and mode, but this fact does not directly explain the formula; it's an observed pattern.

This question belongs to: Accountancy and Statistics Statistics
Question #3
If attributes A and B are positively associated, then (AB) is:
A. Greater than (A)(B)/N
B. Equal to (A)(B)/N
C. Zero
D. Less than (A)(B)/N

Correct Answer: Option A


Explanation:
Positive association means observed joint frequency exceeds independence expectation.

This question belongs to: Accountancy and Statistics Statistics