The mean of 14 observations is 11. One more observation is included and the new mean becomes 12. The $$15^{th}$$ observation is
The mean of 14 observations = 11
⇒ Sum of 14 observations = 11 × 14 = 154
Let the 15th observation be ‘x’.
⇒ (154 + x)/15 = 12
⇒ 154 + x = 12 × 15 = 180
⇒ x = 180 - 154 = 26
∴ The 15th observation = 26
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