Ch. 2.2: Frequency Distributions
Class Width
The difference between two consecutive lower class limits or two consecutive lower class boundaries in a frequency distribution (example pg. 47).
Upper Class Limits
The largest numbers that can belling to the different classes.
Class Boundaries
The numbers used to separate the classes, but with out the gaps created by class limits (example pg. 47).
Gaps
The presence of _______ can show that we have data from two or more different populations (example pg. 51).
Lower Class Limits
The smallest numbers that can belong to the different classes.
Normal Distribution Characteristics
1) The frequencies start low, then increase to one or two high frequencies, then decrease to a low frequency. 2) The distribution is approximately symmetric, with frequencies preceding the maximum being roughly a mirror image of those that follow the maximum (example pg. 50).
Relative Frequency Distribution
A variation of the basic frequency distribution. In a relative frequency distribution, the frequency of a class is replaced with a relative frequency (a proportion) or a percentage frequency (a percent). The sum of the relative frequencies in a relative frequency distribution must be close to 1 (or 100%). *NOTE: when percentage frequencies are used, the relative frequency distribution is sometimes called a percentage frequency distribution. (example pg.49)
frequency
The _______ for a particular class is the number of original values that fall into that class.
Cumulative Frequency
The cumulative frequency for a class is the sum of the frequencies for that class and all previous classes (example pg.49).
Class Midpoints
The values in the middle of the classes. Each class midpoint is found by adding the lower class limit to the upper class limit and dividing it by 2 (example pg. 47)
Frequency Distribution (or frequency table)
shows how a data set is partitioned among all of several categories (or classes) by listing all of the categories along with the number of data values in each of the categories
