Statistical Sciences 2035 Lecture Notes - Confidence Interval, City Newspaper, Categorical Variable
1 Mar 2014
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Document Summary
Confidence intervals for a population proportion (section 7. 4) Studies often examine categorical data: categorical data consists of counts (x) or percents (proportions, p) obtained from counts, this section presents ci"s for the unknown proportion of success, p, of a population. Select a random sample of size n from a population and record the count, x, of successes x ~ bin( n, p) where p = probability of success. We are interested in estimating p, as it is often unknown. To do this, we use our sample and calculate the sample proportion of success p = x n. We know that p will not be equal to p. Instead it will be best to give a confidence interval for which we are confident that the value of p lies in. Shape: approximately normal if n is large : to see if this normal assumption is valid, you must check: np .
