NAME

STAT 291 - Statistics for the Mathematical Sciences I

Making a Histogram

1. Choose the number of categories to use. The following table is a general guide that we will

use.

Sample Size Number of Categories



15 Too small

16 { 31 5

32 { 63 6

64 { 127 7

128 { 255 8

256 { 511 9

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2. Find the range, that is, the largest observation minus the smallest.

3. Divide the range by the number of classes, and truncate the answer to the same accuracy as

the data. Then add one to the last digit of this number.

4. Start the rst category 1

=

2 unit below the rst observation. The following table explains this.

Accuracy \Units" 1

=

2 unit

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Tens 10 5

Ones 1 .5

Tenths .1 .05

Hundredths .01 .005

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5. Complete the categories by adding the number found in step three to the number from step

four to get the right boundary of the rst category. Continue adding to complete the necessary

number of categories.