Statistics for Social Workers Chapter 2 Frequency Distribution/ Graphs

Frequency distribution

reports the number of times each attribute appeared within the sample

line diagram

sometimes used instead of bar graph. Length of line reflect frequencies. Lines usually run horizontally with different labels used for the attributes

absolute frequency distribution table (simple frequency distribution)

table that displays the number of times that each attribute of a variable occurred within a data set. simply count the number of times each attribute occurred and place the total next to that attribute

pie chart

used for nominal level of measurement. shows each data point in proportion to the whole data series as a slice in a circular pie

graphs

A visual representation showing how 2 or more sets are related to each other.

stem and leaf plot

a graph consisting of numbers that reflect the actual case values of all cases in a frequency distribution

x-axis

abiscissa or horizon line the horizontal axis on a coordinate plane

bar graph

also called bar chart. method of dispaying the distribution or frequencies for the attributes of a nominal level variable

cumulative percentage frequency distribution tables

combines the features of cumulative frequency and percentage distribution tables by displaying a column that reports cumulative percentages for each attribute

cumulative frequency distribution table

constructed if the data for a variable is ordinal or higher level of measurement. A data table that contains the number of values that occur at or before ( or below) each value of a variable

frequency polygons

curved shape, a kind of picture, that reflects the overall distribution of the attributes within a data set; not for use with nominal, for use with interval or ratio level data.

grouped frequency distribution

grouping attributes by same size groups with equal gaps. Use when displaying large numbers of cases in groups of 5 to 20 intervals. each value or observation belongs to 1 interval only. Group by reasonable association or like attributes (IE 9-10 are more similar in age than 9-13 year olds)

grouped cumulative percentage distribution

groups data into same size groups and then reports cumulative percentage for each group

percentile ranks or percentile

indicates the percentage pf cases within a group whose attribute falls below a particular score. IE a score on a BDI of 16 has 91.5 % of cases fall below that value. 16 in then in the 90th percentile or 90 is the percentile rank for 16 (rounded to nearest whole number).

array

ordering of every attribute of a variable that occurred within the raw data set, from lowest or smallest to highest or largest- used for ordinal or higher level variables

y-axis

ordinate and vertical line The vertical axis of an axes-type graph.

point of origin

point at which x and y axis meet

histograms

useful for displaying ordinal or higher-level data. They cannot be used with nominal level data. Look like bar graphs but unlike bar graphs, the bars touch each other; Vertical bars of equal width representing frequencies - joined bars

percentage frequency distribution table

uses the absolute percentage column on the far right hand side. Take the absolute frequency number for attribute and divide by the number of cases and x by 100. For example, if there are 20 total cases, and a certain attribute has an absolute frequency of 2, the percentage frequency table would show 10% for absolute percentage for that attribute, because 2/20=.10 X 100= 10%