STATISTICS | JEE Main Concepts Part 1 | Properties of Mean | JEE Main 2013, 2014, 2015 - Videos


In this video, we will learn questions based on Properties of Mean which came in JEE Main Exam in the year 2013, 2014, 2015 from the Topic STATISTICS.
We will discuss some important properties of mean and fast methods to apply those properties in the exam.
If each observation is multiplied / divided by n, then Mean gets multiplied / divided by n2
If a constant number n is added / subtracted to each observation, then the new mean is equal to old mean add / subtract n

Questions Discussed
JEE Main 2013
The mean of a dataset consisting of 20 observations is 40. If one observation 53 was wrongly recorded as 33, then the correct mean will be:
(A) 41 (B) 49 (C) 40.5 (D) 42.5
Answer: (A)

JEE Main 2013
In a set of 2n distinct observations, each of the observations below the median of all the observations is increased by 5 and each of the remaining observations is decreased by 3. Then the mean of the new set of observations:
(A) increases by 1 (B) decreases by 1 (C) decreases by 2 (D) increases by 2
Answer: (A)

Extra Question Discussed
If x ̅ be the mean of x1, x2 , … , xn then for a≠0, the mean of ax1, ax2,… , axn, x_1/a,x_2/a,……,x_n/a is
(A) (a+1/a) x ̅ (B) ((a+1/a) x ̅)/2 (C) ((a+1/a) x ̅)/2n (D) ((a+1/a) x ̅)/n

JEE Main 2015
The mean of the data set comprising of 16 observations is 16. If one of the observation valued 16 is deleted and three new observations valued 3, 4 and 5 are added to the data, then the mean of the resultant data, is
(A) 16.8 (B) 16.0 (C) 15.8 (D) 14.0
[Answer (D)]

JEE Main 2015 Online
A factory is operating in two shifts, day and night, with 70 and 30 workers respectively. If per day mean wage of the day shift workers is Rs. 54 and per day mean wage of all the worker is Rs. 60, then per day mean wage of the night shift workers (in Rs.) is
(A) 75 (B) 69 (C) 66 (D) 74
[Answer (D)]

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