PSY200 CH13 - 13 Two assumptions of parametric statistical...

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13 Two assumptions of parametric statistical tests : statistical tests of null hypothesis based on estimation of population parameters (mu and sigma 2 ) o Type of distributions found in samples— assumption of normality of means o Kind of numbering systems used— assumption of homogeneity of variance 1 st assumption: four components have to be true: — assumption of normality of means o Distribution of sample means has to fit a normal curve—symmetrical, nicely curved, single high point o Standard deviations of samples we’re comparing have to be equal o Research participants have to be randomly selected from population o Experimental error must be randomly distributed across all samples First 2 are statistical, last 2 are dependent on experimenter’s ability for random selections and run experiment with appropriate measurements EXCEPTIONS: not normal curves o Skew = nonsymmetrical curve Skewed (tailed toward) to left = negative skew Skewed to right = positive skew o Kurtosis = shape of the peak of a distribution Platykurtic = flat like rectangular distribution Leptokurtic = sharp like j-shape distribution o Polymodality = values in curve spread out around more than one = more than one
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This note was uploaded on 11/02/2011 for the course PSYCHLOGY 200 taught by Professor Ackroff during the Spring '11 term at Rutgers.

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PSY200 CH13 - 13 Two assumptions of parametric statistical...

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