JEE Main 2018MathematicsStatisticsEasyMCQ

JEE Main 2018 — Statistics Question with Solution

JEE Main 2018 (16 Apr Online)

Question

The mean and the standard deviation S.D. of five observations are 9 and 0, respectively. If one of the observation is increased such that the mean of the new set of five observations becomes 10, then their S.D. is

Choose an option

Show full solutionCorrect option: B
Correct answer
B2

Step-by-step explanation

x¯=∑xin=9

s.d=∑xi-x¯2n=0

⇒xi=x¯∀i

∴ each term in the original observation is 9

⇒ observation 1={9,9,9,9,9}

x¯new =∑xin=9+9+9+9+x55

⇒10=36+x55

⇒x5=14

⇒ new set of observations ={9,9,9,9,14}

s.dnew =∑xi-x¯new2n

=(9-10)2+(9-10)2+(9-10)2+(14-10)25

=4+425

=205=2

Practice this on the real CBT interface

Solve this JEE Main question (and the rest of the Statistics chapter) on PrepSharp's TCS iON-style CBT player — with timer, bookmarks and session analytics.

Solve interactively →

About this question

This is a previous-year question from JEE Main 2018, covering the Statistics chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.