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Unformatted text preview: Large sample 100(1 )% C.I. for I The largesample 100(1 )% confidence interval for is x z / 2 x = x z / 2 n where z / 2 is the z value with an area / 2 to its right and x = / n . The parameter is the standard deviation of the sampled population and n is the sample size. Remark: When is unknown and n is large (say, n 30), the confidence interval is approximately equal to x z / 2 s n where s is the sample standard deviation. Exercise 12.2 from last lecture I A random sample of 90 observations produced a mean x = 25 . 9 and a standard deviation s = 2 . 7. a. Find a 90% confidence interval for b. Find a 99% confidence interval for Smallsample confidence interval I There are many actual needs to address small samples. For example, Federal legislation requires pharmaceutical companies to perform extensive tests on new drugs before they can be marketed. After testing on animals, and if it seems safe, then the company can try it out on humans....
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This note was uploaded on 06/06/2011 for the course STAT 515 taught by Professor Zhao during the Spring '10 term at South Carolina.
 Spring '10
 Zhao
 Standard Deviation

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