PrepRung
Sign inSign up free

NDA 2017 Maths · Mathematics · Statistics · hard

The variance of the observations 2,4,6,8 is 5. If each observation x is changed to 3x+2, the variance of the new set is

Single correct option

The variance of the observations 2,4,6,82,4,6,8 is 55. If each observation xx is changed to 3x+23x+2, the variance of the new set is
  1. A. 55
  2. B. 1515
  3. C. 4747
  4. D. 4545
Show answer and solution

Answer: (D) 4545

Adding a constant does not change variance, but multiplying by 33 multiplies variance by 32=93^2=9. So the new variance is 9×5=459\times5=45. Using 33 instead of 99 gives 1515, ignoring the scale gives 55, and adding 22 to the variance gives 4747.
Report a mistake

Original question written in the NDA 2017 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake