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. Author manuscript; available in PMC: 2008 Oct 2.
Published in final edited form as: Reprod Biomed Online. 2002;4(2):133–139. doi: 10.1016/s1472-6483(10)61930-x

Table 3.

Definitions and procedures used in statistical analysis.

Number of patients in the study: 102 Caucasian women
Pregnancy success: 57 patients who had a live birth
Pregnancy failure: 45 patients who did not have a live birth
Step 1. Probability of pregnancy success (S) was calculated by dividing the number of patients with the presence of the PCR band who had a live birth by 57.
Step 2. The variance of S was calculated as Var(S) [S ×(1−S)]/57.
Step 3. Probability of pregnancy failure (F) was calculated by dividing the number of patients with the presence of the PCR band who did not have a live birth by 45.
Step 4. The variance of F was calculated as Var(F) = [F×(1−F)]/45.
Step 5. The difference (D) of success (S) and failure (F) was found by D = S − F.
Step 6. The standard deviation (SD) of the difference was calculated by: SD = square root of [Var(S) + Var(F)].
Step 7. The probability of the difference, P(z), was found by dividing D by SD and the P-value was found by looking up P(z) in a normal distribution probability table (Weiss, 1995).