Combined Standard Deviations.

⏺️Combined Standard Deviations:-
👉Calculating standard deviation of two
or more series is known as Combined
Standard Deviation.
Where,
\sigma_{1,2} = Combined Standard Deviation of two groups
\sigma_{1} =Standard Deviation of first group
\sigma_{2} = Standard Deviation of second group
d_1^2=(\bar{X_1}-\bar{X}_{1,2})^2
d_2^2=(\bar{X_2}-\bar{X}_{1,2})^2
\bar{X}_{1,2} = Combined Arithmetic Mean of two groups
\bar{X}_1 = Arithmetic Mean of first group
\bar{X}_2 = Arithmetic Mean of second group
n_1 = Number of Observations in the first group
n_2 = Number of Observations in the second group

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