Since bar graphs visually display information, the starting
point and interval of the scale are
very important. Choosing the scale is much more important than
simply making the graph fit on the paper. The starting point and
interval can be changed to make a graph look different, although
the data it is presenting is actually unchanged. For example,
scale can be altered to make bar heights seem dramatic or to make
them seem insignificant.
Where Does the Scale Begin? 

Both graphs below contain the same information. Compare the two. Look at how the scale of the frequency axis can make a difference in the presentation of the information.
Sales for Company X
for the Fourth Quarter1995 
Sales for Company X
for the Fourth Quarter1995 
Note the scale in the graph above:

Note the scale in the graph above:

Interval of the Scale 

Suppose a store manager wants to entice her employees to make more sales. Most sales people usually make around 40 sales per month but the manager wants each person to increase sales to 50 per month. She decides to present a bar graph that shows the average commission made per month on sales. Which graph below will more likely provide more incentive for increasing sales?
Notice that Figure B makes the increase
in commission from $100 to $170 look bigger than in Figure A.
The store manager would want her employees to see Figure
B. It would be more effective in enticing employees to
strive for 50 sales per month.
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