Biology 2244A/B Chapter Notes - Chapter 20: Sampling Distribution, Confidence Interval, Standard Deviation
25 Dec 2016
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Two sample t methods: used for comparing means of populations. Srs from each population or responses from 2 treatments in completely randomized experiment. Subscript shows which group a parameter or statsitic describes. Compare populations: di inference about the difference between population proportions. 20. 2: the sampling distribution of a difference between proportions. When 2 random variables are normally distributed, the variable difference also follows a normal distribution. Center: the difference between the 2 variables" means. Variance: the sum of the 2 variables" variances. When sample large, distribution of p^1-p^2 is approximately normal. Difference between sample proportions is an unbiased estimator of the difference between population proportions. One option: replace population proportions with sample proportions. Standard error: results, as estimate of the standard deviation of the sampling distribtuion. Observed difference between sample proportions: can reflect actual difference, or due to chance variation. Alternative hypothesis: says what kind of difference we expect.
