VOCABULARY TERMS:
CHAPTER 4
unit
 the item or object we observe
subject
 unit is a person
observation
 information or characteristics recorded for each unit
variable
 characteristic that can vary from unit to unit
data set
 collection of observations on one or more variables
qualitative variables
 (aka categorical variables) classify units into categories.
Categories may or may not have a natural ordering.
quantitative variables
 have numerical values that are measurements (length, weight,
etc) or counts (of how many).
discrete variable
 able to count number of possible values
continuous variable
 able to take on any value within a given integral
distribution (of a variable)
 provides possible values that a variable can take on and
how often these possible values occur. Shows the pattern of variation of the variable
Graphical ways to display distribution:
quantitative frequency plots, stemandleaf plots, histograms, time plots, scatterplot
pie chart
 displays the distribution of a qualitative variable by dividing a circle into
wedges corresponding to the categories of the variable such that the size of each wedge is
proportional to the percentage of items in that category
bar graph
 displays the distribution of a qualitative variable by listing the categories of
the variable along one axis and drawing a bar over each category with a height (or length)
equal to the percentage of items in that category. Bars should be of equal width.
frequency table
 way to present data on two qualitative variables
marginal distribution of the row variable
 found by computing the percentage of each
row total based on the grand total (the entire sample size)
marginal distribution of the column variable
 found by computing the percentage of
each column total based on the grand total
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 given the column variable, found by
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 Fall '07
 FAN
 Variance, Probability theory, possible values, variable X. values

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