. 2020 Jan 24;7:450. doi: 10.3389/fbioe.2019.00450

Table 2.

Formulas for merging data of two groups.

	G1	G2	G1 + G2
Sample Size	N₁	N₂	N₁ + N₂
Mean Value	m₁	m₂	$\frac{N_{1} m_{1} + N_{2} m_{2}}{N_{1} + N_{2}}$
Standard Deviation	σ₁	σ₂	$\sqrt{\frac{(N_{1} - 1) σ_{1}^{2} + (N_{2} - 1) σ_{2}^{2} + \frac{N_{1} N_{2}}{N_{1} + N_{2}} (m_{1}^{2} + m_{2}^{2} - 2 m_{1} m_{2})}{N_{1} + N_{2} - 1}}$