Group A contains 20 observations with a mean of 15, while Group B contains 30 observations with a mean of 25. What is the combined mean?
Correct answer: B. 21
- A. 20
- B. 21
- C. 22
- D. 24
Explanation
The combined total is (20 × 15) + (30 × 25) = 1,050, and the combined number of observations is 50. Dividing 1,050 by 50 gives a combined mean of 21.
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About Measures of Central Tendency and Dispersion
Central tendency includes mean, weighted mean, median and mode for raw and grouped data. Dispersion covers range, quartiles, interquartile range, variance, standard deviation and coefficient of variation, including the effect of changes in scale and the distinction between a representative centre and the spread around it.
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