stat 2300 chapter 2

frequency distribution

frequency distribution

a graphical representation of measurements arranged by the number of times each measurement was made

relative frequency distribution

A tabular summary of data showing the fraction or proportion of observations in each of several nonoverlapping categories or classes.

relative frequency

the fraction or percent of the time that an event occurs in an experiment, take the frequency in a category and divide by the total number of observations

bar graph

height of each bar is either the freq. or the relative freq. of the category

pareto chart

Categories are displayed in descending order of frequency, tallest to shortest

pie chart

a type of graph in which a circle is divided into sectors that each represent a proportion of the whole. useful when showing the division of all possible values of a qualitative variable, emphasis on comparing the part as a whole

bar graphs

Useful when comparing two specific different quantities or when tracking change over time, NOT necessarily on the part as a whole

dot plot

a graphical device that summarizes data by the number of dots above each data value on the horizontal axis better for small data sets

stem and leaf plot

A method of graphing a collection of numbers by placing the "stem" digits (or initial digits) in one column and the "leaf" digits (or remaining digits) out to the right. better fit small data sets

histogram

A graph of vertical bars representing the frequency distribution of a set of data. better for large data sets, more sophisticated

classes

largest data - smallest data / # of classes (5-20)

Symmetry

if left and right sides of the graph are approximate mirror images

skewed right

if the right side of the graph extends much further out than the left

skewed left

if the left side of the histogram extends much farther out than the right side

unimodial

graph having 1 peak

bimodial

graph having 2 clear peaks

uniform

frequency of each class is relatively the same

bell-shaped

Which shape of distribution is unimodal and symmetrical at the center?