1. No category

Ages of US Presidents
at Inauguration
57
61
57
57
58
57
61
54
68
51
49
64
50
48
65
52
56
46
54
49
51
47
55
55
54
42
51
56
55
51
54
51
60
61
43
55
56
61
52
69
64
46
54
a) Your first class interval will
start with the multiple of
your class size that is less
than the low of your data
b) Make up your classes
using your class size until
you get to the multiple of
your class size above the
high of your data (If your
high is a multiple of your
class size, you must go one
multiple higher.)
3) Set up a frequency
distribution using your
chosen class interval size:
Since you want between 5 and 12
classes, divide the range by 5 and 12
to determine possible class sizes (use
10 and 25 for very large sets of data)
Range ÷ 12 ≤ class size ≤ Range ÷ 5
2) Find a good class
interval size:
1) Find the range:
High - Low=
X
40-44
44-48
48-52
52-56
56-60
60-64
64-68
68-72
Total
ƒ
2
3
9
11
8
5
3
2
43
6) Add the totals.
Remember: Σƒ=n
5) Find the relative
frequency for each
class (if desired).
rƒ
0.046512
0.069767
0.209302
0.255814
0.186047
0.116279
0.069767
0.046512
1.00
Don't forget to title and label
your graph!!
Draw in the bars neatly to size.
Scale the y-axis to start at 0 and
ending just above the highest
frequency or relative frequency
(depending on which you are
making)
Along the x-axis place the class
boundaries to scale.
7) Take some graph paper.
4) Determine the frequency for each class.
(Remember that 40 - 44 includes all
numbers 40 ≤ x < 44)
Example:
The multiple of 4 that is
less than 43 is 40 and
the multiple of 4 above
69 is 72, so my classes
will go 40-44, 44-48, ...,
68-72
Nice class interval sizes
for this set of data would
be 3, 4, or 5. For this
example I chose to use 4.
Example:
26 ÷ 5 = 5.2
26 ÷ 12 = 2.166667
Example:
69 - 43 = 26