STAT 3460 Lecture Notes - Lecture 7: Confidence Interval, Prediction Interval
14 Mar 2016
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Conidence interval an interval that is constructed that is likely to cover the populaion mean: p( N ) = z the z-value that corresponds to . The interval either does or does not contain , (but we don"t know which, since we don"t know ) Factors that afect conidence intervals: changing n. As n decreases, the interval widens: changing level of conidence. If n is large, can be replaced by s. A machine produces metal rods used in an automobile suspension system. A random sample of 30 rods is selected, and the diameter is measured. The mean diameter is 8. 234 mm and the variance is 0. 00064. 95% conidence = 0. 05 z /2 = z0. 025 = 1. 96. Suppose we want a 98% conidence level that the mean is within 0. 01 of the mean diameter. = 0. 02 n = (2. 325) w = 0. 01 z /2 = 2. 325. One sided conidence intervals: lower conidence bound, upper conidence bound.
