In an experiment with 250 trials, the first 150 trials has mean 16 and standard deviation 4. The overall experiment has mean 15.6 and variance 13.44.The standard deviation of the next 100 trials of given experiment is
A
3
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B
4
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C
6
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D
7
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Solution
The correct option is A3 Given first 150 trials with mean ¯x=16 and standard deviation σx=4
overall 250 trials with mean ¯z=15.6 and standard deviation σ2z=13.44
Let the next 100 trials has mean ¯y and standard deviation σy ∴¯z=∑xi+∑yi250 ∵∑xi=150×16=2400 ∴15.6=2400+∑yi250⇒∑yi=1500
Therefore, mean ¯y=1500100=15