STAT 2040 Chapter Notes - Chapter 8: Confidence Interval, Normal Distribution, Simple Random Sample
11 Oct 2016
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There are two main types of statistical inference procedures: confidence intervals and hypothesis testing. Confidence intervals: a range of plausible values for a parameter, calculated using sample data. Example: telephone polls asking american citizens if they approve or disapprove of the way the president is handling his job (approval rating). 1500 responses: let"s say 645 people approved of the president out of a total sample size of 1500. The sample proportion (p hat) (cid:1868) = (cid:2874)(cid:2872)(cid:2873)(cid:2869)(cid:2873)(cid:2868)(cid:2868)=(cid:882). (cid:886)(cid:885) estimates the population. Point estimate: a single value that is an estimate of a parameter: point estimates are not considered to be sufficient information and require a measure of how uncertain they are to be useful. This is why they are often accompanied by confidence intervals. The quantity 0. 03 is called the 95% margin of error. 0. 43 0. 03 is a confidence interval for p. this can also be written as (0. 40,0. 46)
