Please see below the table generated in Epidata analysis and note the confidence interval in the first row
HIV results Total 1539 108 7.0 (5.8-8.4)
This is the proportion of HIV infected among a group of TB suspects which is 7% with 95% CI being 5.8 - 8.4.
It can be deduced that the upper limb of confidence interval(which is 1.96 times Standard error) is 8.4 minus 7 = 1.4
Similarly, it can be deduced that the lower limb of confidence interval(which is 1.96 times Standard error) is 7 minus 5.8 = 1.2
*Query - why are the two limbs of the confidence interval different?* the same observation can be noted in all CIs noted above in the table. The asymmetry of limbs of CI are expected in case of non-linear measures like Odds Ratio, Relative risk, Hazard Ratio etc, but not in case of simple proportions. I am given to understand (from Dr Hans Reider, from whom I learnt Epidata) that EpiData Analysis is purported to follow the recommendations by the BMJ in the calculation of most confidence intervals and this would indeed suggest that the CI around a proportion should be symmetric on a linear scale.
Would be grateful if you could clarify.
Regards, Ajay