Statistics Examples

12

$12$ ,

23

$23$ ,

45

$45$ ,

56

$56$ ,

78

$78$ ,

89

$89$ ,

n = 4

$n = 4$

Step 1

Find the data range by subtracting the minimum data value from the maximum data value. In this case, the data range is

89 - 12 = 77

$89 - 12 = 77$ .

77

$77$

Step 2

Find the class width by dividing the data range by the desired number of groups. In this case,

\frac{77}{4} = 19.25

$\frac{77}{4} = 19.25$ .

19.25

$19.25$

Step 3

Round

19.25

$19.25$ up to the nearest whole number. This will be the size of each group.

20

$20$

Step 4

Start with

12

$12$ and create

4

$4$ groups of size

20

$20$ .

\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 \\ 32 - 51 \\ 52 - 71 \\ 72 - 91 \end{array}

$\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 \\ 32 - 51 \\ 52 - 71 \\ 72 - 91 \end{array}$

Step 5

Determine the class boundaries by subtracting

0.5

$0.5$ from the lower class limit and by adding

0.5

$0.5$ to the upper class limit.

\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 \\ 32 - 51 & 31.5 - 51.5 \\ 52 - 71 & 51.5 - 71.5 \\ 72 - 91 & 71.5 - 91.5 \end{array}

$\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 \\ 32 - 51 & 31.5 - 51.5 \\ 52 - 71 & 51.5 - 71.5 \\ 72 - 91 & 71.5 - 91.5 \end{array}$

Step 6

Draw a tally mark next to each class for each value that is contained within that class.

\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 & | | \\ 32 - 51 & 31.5 - 51.5 & | \\ 52 - 71 & 51.5 - 71.5 & | \\ 72 - 91 & 71.5 - 91.5 & | | \end{array}

$\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 & | | \\ 32 - 51 & 31.5 - 51.5 & | \\ 52 - 71 & 51.5 - 71.5 & | \\ 72 - 91 & 71.5 - 91.5 & | | \end{array}$

Step 7

Count the tally marks to determine the frequency of each class.

\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 & 2 \\ 32 - 51 & 31.5 - 51.5 & 1 \\ 52 - 71 & 51.5 - 71.5 & 1 \\ 72 - 91 & 71.5 - 91.5 & 2 \end{array}

$\begin{array}{c} Class & Class Boundaries & Frequency \\ 12 - 31 & 11.5 - 31.5 & 2 \\ 32 - 51 & 31.5 - 51.5 & 1 \\ 52 - 71 & 51.5 - 71.5 & 1 \\ 72 - 91 & 71.5 - 91.5 & 2 \end{array}$

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