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26 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is a parameter?
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The summary measure calculated for population data.
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What is a statistic?
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The summary measure calculated for sample data.
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What is a population?
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All elements whose characteristics are being studied.
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What is a sample?
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A portion of the population that is selected for study.
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Part of a bigger picture...
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What is a qualitative variable?
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-categorical
-does not contain numbers but rather data that can fit into 2 or more non-numerical categories |
think qualitative vs. quantitative
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What is a quantitative variable?
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-numerical, numeric values assigned
-can be discrete or continuous |
think quantitative vs. qualitative
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What is a discrete variable?
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-quantitative variable
-contains a certain value with no intermediate values ie. integers, grades |
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What is a continuous variable?
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-quantitative variable
-numerical value over a certain interval or intervals ie. GPA, gas prices |
continuous, like continuing over a range
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What does a histogram show?
Compared to boxplots, what does it represent? |
-number of modes (unimodal or bimodal)
-tail weight -shape (symmetry and skew) -->skewness is identified by looking at TAIL -compared to boxplots, best representation of MODALITY |
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What does a boxplot show?
Compared to histograms, what does it represent? |
-outliers
-shape (symmetry and skew) -->skewness is identified by looking at GRAPH WITHIN ITSELF or GRAPH AS A WHOLE -compared to histograms, best representation of SKEWNESS |
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What is an outlier?
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An observation that falls well above or well below (more than three standard deviations) the bulk of the data.
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What is the median?
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The value of the midpoint of a data set that has been ranked in order (increasing or decreasing)
If dataset has an even number of values, take the average of the two middle values. |
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What is the mean?
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The average of all the values.
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What is the mode?
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The most frequent value in a dataset.
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Graphically, relating MEAN and MEDIAN, how is SYMMETRY shown?
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median = mean
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Graphically, relating MEAN and MEDIAN, how is LEFT SKEW shown?
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median > mean
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Graphically, relating MEAN and MEDIAN, how is RIGHT SKEW shown?
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median < mean
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What is affected by the 'Outlier effect'?
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-mean
-median is resistant |
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What is variance?
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The average of squared deviations.
-never negative -square the original units -uses (n-1) degrees of freedom to account for the remaining observations. |
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What is Standard Deviation?
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The square root of variance. The larger is is, the larger is the spread of the data.
-never negative |
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What is a scatterplot?
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A graphical display of 2 quantitative variables (x=explanatory, y=responding)
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What is correlation? Is it sensitive to outliers? What relationship does it assume?
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Summary measure that describes the strength of linear association.
'r' - (-1<r<1) r>1 = positive linear r<1 = negative linear closer to 0, less association. -sensitive to outliers. -assume STRAIGHT LINE relationship |
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What does R-squared represent?
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The proportion in variation of y explained by x.
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What is a residual? When is it significant?
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The prediction error, the difference between the observed and predicted value. The closer it is to zero, the less difference there is, so the better is the prediction.
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What is an observational study?
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Researcher observes characteristics of subjects in samples from populations of interest.
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key word: OBSERVational
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What is an experimental study?
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Researcher applies different treatments to different subjects and observes the outcomes.
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key word: EXPERIMENTal
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