STATS 250 Lecture Notes - Lecture 6: Standard Score, Standard Deviation, Test Statistic
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Phat +/- z* (cid:523)s. e. (cid:523)phat(cid:524)(cid:524) is the general confidence interval where we"re estimating a. )t"s not conservative and it"s flexible in that it lets you be whatever level of confidence you want. The z* multiple is dependent on whether you want to be 90 or 99% The general conservative formula, which lets you be as confident as you want, is given by phat +/- z*/2squareroot (n) This is how you get the 95% conservative interval because if you let z*=2, you get. These are the formulas for estimating our population proportion with our data. The conservative confidence interval is a nice interval because it will have a margin of error that might be a little overestimating but it will never be underestimating. Slide 14: conservative confidence interval (z*/2square root (n)) Doing the algebra, you can find the sample size needed for a certain level of confidence and a certain margin of error.