stats ch2 mean, sd, z-scores

stats ch2 mean, sd, z-scores - The Mean Variance and...

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The Mean, Variance, and Standard Deviation The primary numbers used to describe a distribution of scores when not using a picture.
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Mean The mean is an average score known as a measure of central tendency . The mean is used to represent a whole set of data with one number. The mean is the single best value for this purpose.
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The Mean – M The mean need not represent an actual, or even a possible value on a variable. The mean uses all the scores in its calculation and is very sensitive to (affected by) extreme scores called outliers. M = ( Σ X)/N ( Σ means sum up, X means all the scores, N is the total number of scores).
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In addition to being the best possible single value representation of a set of data, it is also our best prediction for an individual score if we have no other information available.
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Calculate the mean number of children for our sample. Each family’s score is an X. 0 2 3 1 1 1 2 0 2 2 4 8 Σ X = 0+2+3+1+1+1+2+0+2+2+4+8 = 26 N = 12 M = 26/12 = 2.17
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Other measures of central tendency The median – the middlemost score in a set of ordered scores. Good when a few extreme scores would greatly affect the mean. The mode – the most frequently occurring score in a set of scores. Not affected by a few extreme scores. Good for nominal (qualitative, categorical) variables.
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This note was uploaded on 10/12/2008 for the course PSY 385 taught by Professor Mannes during the Fall '08 term at Widener.

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stats ch2 mean, sd, z-scores - The Mean Variance and...

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