full2.gif (11401 bytes)
Frequency Histogram
(A worked Problem:  Procedure explained in more detail in Chapter 3)

Using the following frequency distribution of 100 IQ scores create a Frequency Histogram:

Real Lim

App Lim

 Freq

Mid Pt

Rel F

Cum F

C R F

Cum %


129.5-134.5
124.5-129.5
119.5-124.5
114.5-119.5
109.5-114.5
104.5-109.5
99.5-104.5
94.5-99.5
89.5-94.5
84.5-89.5
79.5-84.5
74.5-79.5


130-134
125-129
120-124
115-119
110-114
105-109
100-104
95-99
90-94
85-89
80-84
75-79


5
5
5
10
10
15
15
10
10
5
5
5


132
127
122
117
112
107
102
97
92
87
82
77


.05
.05
.05
.10
.10
.15
.15
.10
.10
.05
.05
.05


100
95
90
85
75
65
50
35
25
15
10
5


1.00
.95
.90
.85
.75
.65
.50
.35
.25
.15
.10
.05


100
95
90
85
75
65
50
35
25
15
10
5

I. To create a frequency histogram we use only the Real Limits and the Frequency

II.  Label the axes

    A.  Label the X axis

        a.  It is best to label the X axis with the real limits, beginning with the lowest real limit

        b.  Remember also to provide a label that tells the units (in this case it is IQ)

    B. Label the Y axis

        a.  Begin at 0 if you can and label up to the largest frequency

        b.  Remember to also put the label "Frequency" next to the numeric labels

fh1.gif (8324 bytes)

III.  Next we will plot the first bar

    A.  The height of the bar is equal to the frequency in the interval (for the first interval this is 5)

    B.  The width of the bar is equal to the real limits (for the first bar these are 74.5 and 79.5)

fh2.gif (8944 bytes)

IV.  Then we finish the histogram by plotting the rest of the bars

fh3.gif (13837 bytes)

Hint:  Remember that all the bars are equal width with the X values at the real limits and
            the height at the frequency of the interval. 

Hint:  Remember that the graph is unreadable without  proper labels. 
            If you leave off just one of the labels the entire graph is wrong

Copyright © 2004 by Mark W. Vernoy