STAT 2000 Lecture 15: February 22
23 Feb 2017
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Document Summary
7. 2 how sample means vary around the population mean. Estimate average; x-bar (stat), has a distribution with a shape, center and variation: distribution provides probability for the possible values of the stat. Population distribution: distribution form which we took the sample. Data distribution: distribution of data from one sample (dot plot) Sampling distribution of the sampling mean: distribution of the sample averages. Sampling distribution of the sample mean, x-bar: shape: look at histogram of sample means given; unimodal and symmetric, center: mean of the sampling distribution of x-bar equals the mean of the population, spread: the std. dev. Of x-bar is smaller than the std. dev. Degrees of freedom: specify how close t-curve is to z-curve. If population ((cid:4667) is known find std. normal: (cid:3040)(cid:3032)(cid:3041) If population ((cid:4667) is unknown find t-dist.
