All you have to do is to look up the formula for obtaining combined variance estimate from two sample groups. In that case n1 and n2 (sample sizes) are used as the "weights."
s^2 = (n1 * s1^2 + n2 * s2^2)/(n1 + n2) You should be able to figure out the rest. Ken >I am spacing out on a formula, and my textbooks haven't been too helpful. >Suppose I have 2 groups. What I want to do is come up with a weighted >variance estimate for the combination of the two groups given s1, s2, w1, >and w2. > >I know this is simple. Any help is appreciated. > >Karen Scheltema, M.A., M.S. >Statistician >HealthEast >Research and Education >1700 University Ave W >St. Paul, MN 55104 >(651) 232-5212 (phone) >(651) 641-0683 (fax) >[EMAIL PROTECTED] >. >. >================================================================= >Instructions for joining and leaving this list, remarks about the >problem of INAPPROPRIATE MESSAGES, and archives are available at: >. http://jse.stat.ncsu.edu/ . >================================================================= > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
