Envr301.7

Twosided vs onesided ttests o onesided the mean of

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Unformatted text preview: ost generally: the slope of a given line is different from 0 (which means no relationship between X and Y) • Type 1: Paired (two measures of the same item) o E.g. Before and After. Does heart rate increase after drinking a cup of coffee? Does plant growth increase after adding fertilizer to pots of soil? • Types 2 and 3: Unpaired o E.g. Do MSE students downtown consume more coffee than MSE students at Mac? o Type 2 if we are sure the variances are equal, Type 3 if we are not. • Comparing distributions: concepts o The difference between means of two distributions might be the same even if the variability changes considerably (tighter/looser distributions). o We need to judge the difference to their means relative to the spread or variability of their scores. • Two ­sided vs one ­sided t ­tests o One ­sided: The mean of group 1 is greater than the mean of group 2. Used if we are given clear information about which group is which. o Two ­sided: Used if we know the means of the two groups are different, but we are not sure column of data corresponds to which group, or whether we are “blind” to...
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