Set, Relation and FunctionHard
Question
For two data sets, each of size 5, the variances are given to be 4 and 5 and the corresponding means are given to be 2 and 4, respectively. The variance of the combined data set is
Options
A.

B.6
C.

D.

Solution
σx2 = 4
σy2 = 5
= 2
= 4
∑xi = 10; ∑yi = 20

∑xi2 = 40
∑yi2 = 105


σy2 = 5
= 2
= 4
∑xi = 10; ∑yi = 20
∑xi2 = 40
∑yi2 = 105


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