HOW TO FIND THE CORRECT MEAN FROM INCORRECT MEAN

About "How to find the correct mean from incorrect mean"

How to find the correct mean from incorrect mean :

Here we are going to see how to find the correct mean from incorrect mean.

Example 1 :

The average height of 10 students in a class was calculated as 166 cm. On verification it was found that one reading was wrongly recorded as 160 cm instead of 150 cm. Find the correct mean height.

Solution :

Average height  of 10 students x̄ = 166 cm

Here 166 is the incorrect mean and n = 10

We have x̄ = ∑x / n  =  ∑x / 10 

∑x / 10   =  166

Multiply 10 by both sides

The incorrect ∑x  =  1660

The incorrect ∑x = 1660

The correct  ∑x  

  =  incorrect  ∑x  – the wrong value + correct value

  =  1660 – 160 + 150 = 1650

Hence, the correct A.M. = 1650 / 10

  =  165 cm

Hence the correct mean height is 165 cm.

Example 2 :

The average height of 20 students in a class was calculated as 160 cm. On verification it was found that one reading was wrongly recorded as 132 cm instead of 152 cm. Find the correct mean height.

Solution :

Average height  of 10 students x̄ = 160 cm

Here 166 is the incorrect mean and n = 20

We have x̄ = ∑x / n  =  ∑x / 20 

∑x / 20   =  160

Multiply 20 by both sides

The incorrect ∑x  =  160 (20)  =  3200

The incorrect ∑x  =  3200

The correct  ∑x  

  =  incorrect  ∑x  – the wrong value + correct value

  =  3200 – 132 + 152  =  3220

Hence, the correct A.M.  =  3220 / 20

  =  161 cm

Hence the correct mean height is 161 cm.

Example 3 :

If in a class of 20 students, 5 students have scored 76 marks, 7 students have scored 77 marks and 8 students have scored 78 marks, then compute the mean of the class.

Solution :

Mean  =  Sum of marks of 20 students / 20

5 students have scored 76 marks

7 students have scored 77 marks

8 students have scored 78 marks

  =  [ 5 (76) + 7 (77) + 8 (78) ] / 20

  =  (380 + 539 + 624) / 20

  =  1543 / 20

  =  77.15

After having gone through the stuff given above, we hope that the students would have understood "How to find the correct mean from incorrect mean". 

Apart from the stuff given above, if you want to know more about "How to find the correct mean from incorrect mean".

Apart from the stuff given on this web page, if you need any other stuff in math, please use our google custom search here.

Kindly mail your feedback to v4formath@gmail.com

We always appreciate your feedback.