The mean of five observations x, x + 2, x + 4, x + 6, x + 8 is m. What is the mean of the first three observations?
- A. m
- B. m-1
- C. m-2 ✓
- D. m-3
Correct Answer: C. m-2
Explanation
Since the observations form an arithmetic progression, their mean is the middle term: m = x + 4. The mean of the first three observations (x, x + 2, x + 4) is their middle term, which is x + 2. Since x + 2 = (x + 4) - 2, the new mean is m - 2.
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