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10 Cards in this Set
- Front
- Back
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Statistics
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The art and science of collecting, organizing, describing, analysing and drawing conclusions from data.
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Histogram
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a histogram breaks the range of values of a variable into classes and displays only the count or percent of the observations that fall into each class. *Always choose classes of equal widths*
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Histograms vs. Bar Graphs
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-Histograms shows the frequency of a quantitative variable, while a bar graph displays the distribution of a categorical variable
-Bar graphs have blank spaces between bars to separate the items being compared, while histograms are drawn with no spaces to indicate that all values of the variable are covered |
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"SOCS"
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Shape - skewed left or right, symmetric,
Outliers- observations that stand apart from the body of data, identified by judgement (or Q3 + 1.5 x IQR for boxplots) Center- mean, median, mode Spread- range, IQR, standard deviation |
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Resistant statistics
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Statistics that are not sensitive to the influence of a few extreme observations.
The mean is a NONRESISTANT statistic, while the median is a RESISTANT statistic. |
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5 Number Summary
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1. Minimum
2. Q1 3. Median 4. Q3 5. Maximum |
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Interquartile Range (IQR)
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Q3-Q1
Middle 50% of the data *A more reliable measure of spread than the range when there are suspected outliers |
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Standard Deviation
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-measures spread by looking at how far the observations are from their mean
-the sum of the deviations of the observations from their mean will always be zero *a NONRESISTANT statistic! - std = 0 only when there is no spread/variability, (all observations have the same value) |
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Effect of a linear transformation
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-multiplying each observation by a positive number "B" multiplies both measures of center (mean, median,) and measures of spread (IQR, standard deviation,) by B.
- Adding any number "A" to each observation adds "A" to measures of center and to Q1/Q3, but does NOT affect measures of spread (IQR, Std.) |
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Z-scores
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-tells how many standard deciations away from the mean the original obsercation falls, and in which direction.
z= (observation - mean) / standard deviation |
