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Equal standard deviations 1 2 iii independence

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Unformatted text preview: ons II. Equal standard deviations ($1 = $2) III. Independence Robustness against departures from Normality %e Central Limit %eorem asserts that departures from normality are not serious as long as sample sizes are reasonably large Long-tailed distributions (those with outliers) cause more problems than skewed distributions Robustness against departures from equal standard deviations Having unequal population standard deviations causes more problems than la& of normality If sample sizes are roughly the same, having unequal population standard deviations is not mu! of a problem %e worst situations occur when one sample is mu! larger than the other and the smaller sample comes from the population with the largest standard deviation Robustness against departures from independence La& of independence is usually caused by collecting data in subgroups rather than as individuals (cluster e#ect) collecting more than one observation on a given individual over time (serial e#ect) Special regression or analysis of variance models are used when data are collected in subgroups, time series models are used when o...
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This note was uploaded on 10/03/2011 for the course STAT 511 taught by Professor Eggett,d during the Winter '08 term at BYU.

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