Question

If 7,4 and 9 be the arithmetic mean of three seperate groups containing 6,2 and 5 observations respectively, then calculate the arithmetic mean of  all the thirteen observations combined? 

Answer 1

Solution

From the data given in the question, statistics for observations in the three seperate groups are as follows:

x̅₁ = 7, n₁ = 6;

 x̅₂ = 4, n₂ = 2;  

x̅₃ = 9, n₃ = 5.  

Combined Arithmetic Mean of all 13 observations in the given data is as shown below:

 

So, Combined Arithmetic Mean of all 13 observations in the data is 7.5

Combined Arithmetic Mean of all 13 observations in the data is 7.5