Term
| Variances of independent random variables add |
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Definition
| the variance of a sum or difference of independent random variables is the sum of the variances of those variables |
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Term
| Sampling distribution of the difference between two proportions |
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Definition
| the sampling distribution of p1-p2 is under appropriate assumptions modeled by a Normal model with mean m - p1-p2 and standard deviation SD(p1-p2) = sqrt(p1q1/n1 + p2q2/n2) |
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Term
| Two proportion z-interval |
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Definition
| a two-proportion z-interval gives a confidence interval for the true difference in proportions, p1-p2, in two independent groups; the CI is (p1-p2) +/- z* x SE(p1-p2) where z* is a critical value from the standard Normal model corresponding to the specified confidence level |
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Term
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Definition
| when we have data from different sources that we believe are homogeneous, we can get a better estimate of the common proportion and its standard deviation; we can combine, or pool, the data into a single group for the purpose of estimating the common proportion; the resulting pooled standard error is based on more data and is thus more reliable (if the null hypothesis is true and the groups are truly homogeneous) |
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Term
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Definition
| Test the null hypothesis H0: p1 - p2 = 0 by referring the statistic z = (p1-p2)/SEpooled(p1-p2) to a standard Normal model |
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