9-2 Confidence Interval for the difference between proportions
p1 - p2
p1 - p2
When n·q and n·p are both greater than 5, the binomial distribution is approximated by the standard normal distribution (z distribution).When n·q and n·p are both greater than 5, the binomial distribution is approximated by the standard normal distribution (z distribution).
To find the critical value of z for confidence intervals, compute α ÷ 2 and look up the associated value of z in the standard normal distribution (Table A-2). The critical value for confidence intervals is always positive.
