Hi All,

I am trying to calculate the proportion of two specific variables and compare the difference between these two population proportions. From the table below, In the 67 samples, the proportion of co-infection with vaccine virus is 2/7 (29%), while the proportion of non-vaccine virus with co-infection is 11/60 (18%).
I have chosen the Two-sample test of proportion. I am not sure about the 95% CI for the proportion of the co-infection with vaccine virus. Isn't the possible range of values is 0 to 100%? What will be the right test to workout the CI for the proportion? Many thanks.

Coinfection vaccine virus absent (0) present (1) Total
absent (0) 49 5 54
present (1) 11 2 13
total 60 7 67
code:
. prtest coinfection, by(vaccine)

Two-sample test of proportion 0: Number of obs = 60
1: Number of obs = 7
-----------------------------------------------------------------------------------------------------------------
Variable | Mean Std. Err. z P>|z| [95% Conf. Interval]
---------------+------------------------------------------------------------------------------------------------
0 | .1833333 .0499537 .0854259 .2812408
1 | .2857143 .1707469 -.0489436 .6203721
---------------+------------------------------------------------------------------------------------------------
diff | -.102381 .1779042 -.4510667 .2463048
| under Ho: .1579452 -0.65 0.517
-----------------------------------------------------------------------------------------------------------------
diff = prop(0) - prop(1) z = -0.6482
Ho: diff = 0

Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(Z < z) = 0.2584 Pr(|Z| < |z|) = 0.5169 Pr(Z > z) = 0.7416