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Sherril M. Stone, Ph.D. |
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Department of Family Medicine |
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OSU-College of Osteopathic Medicine |
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Describes data set |
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Affected by outliers |
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Outliers skew central tendency and graphs |
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Mean |
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Median |
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Mode |
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Standard Deviation |
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Population - Greek letter µ |
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Sample - letter of the variable with a bar on
top (X bar) |
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Formula for Mean |
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Xi =
(= 4+7+11+13+13+16+17)/ 7 =
81/7 = 11.5714 @ 11.57
4 |
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7
Note that the computation of the mean is carried |
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11
to four decimals and rounded to two decimal points |
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at the end of the computation. |
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13 |
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16 |
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17 |
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Median |
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When scores are in rank order Ð the data score
that is exactly in the middle of all the scores |
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If there is an even number of data Ð add middle
two scores and divide by 2 |
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Mode |
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Most frequent score |
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May have more than 1 mode |
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Bell-Shaped Ð normal distribution |
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Skewed |
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Positive Ð Mean larger than Median |
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Negative Ð Mean smaller than Median |
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Others |
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Rectangular |
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Bimodal |
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J-curves |
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Notes
