Proportion confidence intervals are the same as x-bar confidence intervals, except we use p-hat and p instead. Use the exact same confidence interval formula:
p-hat +/- crit. val (std. dev) where the std. dev is equal to root(p-hat(1-p-hat)/n)
In most instances, you'll see something like "45 out of 56..." in a problem, so you'll need to use this information to calculate what your p-hat is. The procedure for a proportion confidence interval is the same except for your third assumption, you must check, in regard to sample size:
np-hat >= 10 and n(1 - p-hat) >=10. This verifies the size assumption, so by the Central Limit Theorem, the sample either is or is not sufficiently large.
No comments:
Post a Comment