Carillon Technologies Limited

Steps for Constructing a Histogram

Step #1 Identify and define your problem.

(Our problem is to study the variation in corn flake lengths)

 

Step #2. Collect Data

Collect as many samples as you can, (usually 30) on a checksheet.

Step #3

Collect Data and then determine the largest and smallest sample values.

  

Step #4

Find the range of the data by subtracting the smallest value from the largest value.

R = largest - smallest = 32 mm - 21 mm = 11 mm

  

Step #5 .

Using Sturgis Rule to Determine Cell Width

Example:

n= 40,

R= 11

Cell Width =

Range Multiplier * Range =

Cell Width = 0.1582*11 = 1.74 = 2.0

Sturgis rule = cell width i =

i = R/(1 + 3.322 logn)
Sample Size Range Multiplier
25 0.1772
30 0.1693
35 0.1631
40 0.1582
45 0.1540
50 0.1505
55 0.1475
60 0.1448
65 0.1424
70 0.1403
75 0.1383
80 0.1366
85 0.1350
90 0.1335
95 0.1321
100 0.1308

Step #6.

Determine the class boundaries and class midpoints.

Step #7.

Place each data value in its appropriate class. Record this by placing a "chicken scratch" for every value in the tally column.
 

 

Step #8.

Total the frequencies under each class.

Then total all frequencies.

We have a total of 40 data points; it checks.

Step #9.

Label the vertical scale based on the maximum number of corn flakes in a class.

Then write the class midpoints on the horizontal axis.

Step #10.

Fill in the appropriate number of boxes based on the frequencies.

Then add the specification limits (if you know them) to the chart.

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