Q1 / 77 · NTA Abhyas (JEE Main) 2020 · Mathematics · Statistics

The mean and standard deviation of 50 observations are 50 and 10. Later on, it was decided to omit an observation that was incorrectly recorded as 99. If the variance of the remaining 49 observations is λ49, then the value of λ is equal to

Correct answer: 2550

Solution

x-=∑x150=50
⇒∑xi=2500
Correct ∑xi=2500-99=2401
Correct x-=240149=49
σ2=∑xi2n-x-2
⇒100=∑xi250-2500
⇒∑xi2=130000

Correct ∑xi2=130000-992=120199
Correct σ2=∑xi2n-x-2
=12019949-492
=120199-11764949=255049=λ49

Hence, λ=2550
 

Hence, the correct answer is 2550.

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