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26 Cards in this Set
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What is a parameter?

The summary measure calculated for population data.



What is a statistic?

The summary measure calculated for sample data.



What is a population?

All elements whose characteristics are being studied.



What is a sample?

A portion of the population that is selected for study.

Part of a bigger picture...


What is a qualitative variable?

categorical
does not contain numbers but rather data that can fit into 2 or more nonnumerical categories 
think qualitative vs. quantitative


What is a quantitative variable?

numerical, numeric values assigned
can be discrete or continuous 
think quantitative vs. qualitative


What is a discrete variable?

quantitative variable
contains a certain value with no intermediate values ie. integers, grades 


What is a continuous variable?

quantitative variable
numerical value over a certain interval or intervals ie. GPA, gas prices 
continuous, like continuing over a range


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 


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 


What is an outlier?

An observation that falls well above or well below (more than three standard deviations) the bulk of the data.



What is the median?

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. 


What is the mean?

The average of all the values.



What is the mode?

The most frequent value in a dataset.



Graphically, relating MEAN and MEDIAN, how is SYMMETRY shown?

median = mean



Graphically, relating MEAN and MEDIAN, how is LEFT SKEW shown?

median > mean



Graphically, relating MEAN and MEDIAN, how is RIGHT SKEW shown?

median < mean



What is affected by the 'Outlier effect'?

mean
median is resistant 


What is variance?

The average of squared deviations.
never negative square the original units uses (n1) degrees of freedom to account for the remaining observations. 


What is Standard Deviation?

The square root of variance. The larger is is, the larger is the spread of the data.
never negative 


What is a scatterplot?

A graphical display of 2 quantitative variables (x=explanatory, y=responding)



What is correlation? Is it sensitive to outliers? What relationship does it assume?

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 


What does Rsquared represent?

The proportion in variation of y explained by x.



What is a residual? When is it significant?

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.



What is an observational study?

Researcher observes characteristics of subjects in samples from populations of interest.

key word: OBSERVational


What is an experimental study?

Researcher applies different treatments to different subjects and observes the outcomes.

key word: EXPERIMENTal
