Frequency distribution
a table that shows classes or intervals of data entries with a count of the number of entries in each class
Frequency
the number of data entries in the class
Class width
the distance between lower (or upper) limits of consecutive classes
Range
the difference between the maximum and minimum data entries
Midpoint
the sum of the lower and upper limits of a class divided by two
Relative frequency
the portion, or percentage, of the data that falls in that class
Cumulative frequency
the sum of the frequencies of that class and all previous classes
Frequency histogram
a bar graph that represents the frequency distribution of a data set
Class boundaries
the numbers that separate classes without forming gaps between them
Frequency polygon
a line graph that emphasizes the continuous change in frequencies
Ogive
a line graph that displays the cumulative frequency of each class at its upper class boundary
Measure of central tendency
a value that represents a typical, or central, entry of a data set
Mean
the sum of data entries divided by the number of entries
Median
the value that lies in the middle of the data when the data set is ordered
Mode
the data entry that occurs with the greatest frequency
Outlier
a data entry that is far removed from the other entries in the set
Weighted mean
the mean of a data set whose entries have varying weights
Symmetric
when a vertical line can be drawn through the middle of the graph of the distribution and the resulting halves are approximately mirror images
Uniform
when all entries in the distribution have equal or approximately equal frequencies
Skewed
when the "tail" of the graph elongates more to one said than to the other
Deviation
the difference between the entry and the mean of the data set
Coefficient of variation
describes the standard deviation as a percent of the mean
Z-score
the number of standard deviations a value x lies from the mean