Question

the mean of 10 observations is 12 , later on was taken -5 instead of 5, then find the correct mean

thankyou

Answer 1

Given:

✰ The mean of 10 observations = 12

✰ The value of 5 was wrongly taken as - 5.

To find:

✠ The correct mean.

Solution:

First we will find in correct value of sum of observation as we are provided with the mean of 10 observations. After that we will find the correct value of sum of observation by subtracting the incorrect observation and correct observation from incorrect value of sum of observations. After finding the correct value of sum of observation we will divide it by the number of observations to find out the correct mean.

Let's find it...✧

✭ Mean = Sum of observations/Number of observations ✭

✭ Mean = Σx/n ✭

Putting the values,

➛ Σx/10 = 12

➛ Σx = 12 × 10

➛ Σx = 120

∴ The incorrect value of sum of observations = 120

➛ Correct value of Σx = Incorrect value of sum of observations - Incorrect observation + Correct observation

➛ Correct value of Σx = 120 - ( - 5 ) + 5

➛ Correct value of Σx = 120 + 5 + 5

➛ Correct value of Σx = 120 + 10

➛ Correct value of Σx = 130

Now, at last find out the correct mean

➤ Correct mean = Correct value of Σx/n

➤ Correct mean = 130/10

➤ Correct mean = 13

∴ The correct mean = 13

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