The pooled variance used in Case 2A is defined 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+n2-1))
• C. sqrt((s1^2(n1-1) + s2^2(n2-1))/(n1+n2-3))
• D. sqrt((s1^2(n1-1) + s2^2(n2-1))/(n2+n1-2))

Answer: (A)