chapter 2 unit b E280
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frequency distribution (table) for qualitative data
 groups the data into categories and records how many observations fall into each category
 this can be done Nominal or Ordinal scale data

A frequency distribution (a table that show frequency of accuracy) for quantitative data
 groups the data into numerical intervals called classes , and records the number of observations that fall into each class
 either Interval or Ratio scale

guidelines when constructing frequency distribution (Quantitative data)
Approximating the class width
 Classes are Mutually Exclusive (cannot overlap)
 Classes are Exhaustive (cannot miss a value)
 Largest valueSmallest value
 Number of classes

Cumulative frequency distribution
specifies how many observations fall below the upper limit of a particular class

relative frequency distribution
identifies the proportion or fraction of values that fall into each class
 CRF=Class freq
 total number of observation

histogram
is a visual representation of frequency or a relative frequency distribution

the shape of most data distributions may be categorized as either
 Symmetric a mirror image, same on both side
 skewed (positively skewed right) (negatively skewed left)

ogive
plot the cumulative frequ of each class above the upper limit of the corresponding class

polygon
plot the class midpoints on x axis and associated frequency in y axis

Steam and leaf diagram
 visual display of quantitative (numerical) data it gives an overall picture of the data's center and variability data
 set is separated into two parts; the stem consists of the leftmost
 digit, while the leaf is the last digit that is relevant for data
 distinction

scatterplot
 is uesed to determine if two variables are related
 each point is pairing
 Linear as indicated by an upward or downward sloping trend
 Curvilinear
 no relationship