Confidence intervals for proportions, using Wilson's method. This calculator works off-line. (IE4)

Enter data into the boxes "A" and "B"
Test condition
Present Absent
Total A+B= A = B =
Proportion "A" of "A+B" as a percentgage with confidence intervals = % 95% CI= %

If a representative sample ("A+B") is examined from a population and "A" out of total sample have a particular characteristic, then it can be estimated that the proportion of the total population with this characterisitic will lie somewhwere between the two confidence intervals. 95% of any additional samples taken from this population and analysed in the same way would provide a result which wouldlie between these two confidence intervals.

Reference - Wilson EB. J Am Stat Assoc 1927, 22, 209-212.
Programme written by DJR Hutchon copyright Requires Internet Explorer 4.0 or above (or eqivalent) for calculator to work. This calculator is for educational use. It is believed accurate but no responsibility for accuracy of the results is accepted by the author. David J R Hutchon BSc, MB, ChB, FRCOG Consultant Obstetrician, Memorial Hospital, Darlington, England.