Harris and Hochman proposed a method for calculating the p value for the presence of an antibody. This method is more liberal than Fisher's exact method, requiring less testing to confirm specificity.
Antigen on Cells?
Cells React with Patient Serum?
Designation
yes
yes
A
yes
no
B
no
yes
C
no
no
D
total number of cells tested =
= A + B + C + D
probability that the findings are due to chance
(and not due to the presence of specific antibody) =
= ((A / (total number of cells tested)) ^ (A)) * ((D / (total number of cells tested)) ^ (D))
where:
• (0^0) give problems.
Interpretation:
• A p value < 0.05 is the minimum value required for the interpretation that an antibody to the antigen is present to be considered statistically valid.
• If the p value is >= 0.05, then the findings could be due to another antibody and additional cells need to be tested or an alternative hypothesis considered.
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