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

Explanation:
GRR = Σ (ASFR for female births only) × 5 (for 5-year age groups), measuring the average number of daughters a woman would have, focusing on female offspring for generational replacement analysis.

Explanation:
All are sources that provide demographic data, though census and registration are more traditional.

Explanation:
Population variance = 100/10 = 10. Sample variance would be 100/9≈11.11, but question likely assumes population. I'll specify 'if data is population', but not specified. I'll assume population for simplicity.