The pooled standard deviation is computed as:

The pooled standard deviation is computed as:

• A. sqrt((s1^2(n1-1) - s2^2(n2-1))/(n1+n2-2))
• B. sqrt((s1^2(n1-1) + s2^2(n2-1))/(n1+n2))
• C. sqrt((s1^2(n1-1) + s2^2(n2-1))/(n1+n2-4))
• D. sqrt((s1^2(n1-1) + s2^2(n2-1))/(n1+n2-2))

Answer: (D)