The Method
Kramer, H.H. and C.R. Burnham. 1947. Methods of combing
linkage intensity values from backcross, F2 and F2 genetic
data. Genetics 32:379-390.
Fisher, R.A. 1946. A system of scoring linkage data, with special reference
to the pied factors in mice. Amer. Nat. 80:568-578.
Fisher (1946) - "has presented a simple method of scoring linkage
data based on maximum likelihood formulae which can be used to obtain:
1) a test of significance of the deviations from independent assortment
for each source of data as well as for the pooled data, 2) a test of
the homogeneity of the group of linkage intensities to be combined,
adn 3) the average or combined p value." Kramer and Burnham (1947).
There are two ways to combine data from several types of families to
get the overall estimate of p. We can weight the individual estimates
of each type of family, using the total amount of information from each
family.
combined p value by weighting = 
We already showed this method in the last section. An alternative method
of obtaining a combined estimate of p is Fisher's Scoring Method.
Fisher's score for each type of family can be used
to obtain a combined estimate of 
.
The general formula for obtaining a score for each type
of family is obtained from the unreduced maximum likelihood
equations, substituting p=1/2.
