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If mean and standard deviation of 5 observations x 1 , x 2 , x 3 , x 4 , x 5 are 10 and 3, respectively, then the variance of 6 observations x 1 , x 2 , ….., x 5 and –50 is equal to

1. 582.5
2. 507.5
3. 586.5
4. 509.5

Correct answer: 507.5

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