the number of sets sold. Notice how striking your
original report is getting to be. The 1930 sales average towers
far above 1929, and 1929 above the previous years.
Or instead of drawing in blocks representing individual
sets, he may use specially prepared paper already ruled off in
blocks. Then he selects a vertical line and marks off on this,
divisions representing sets sold. Each division represents one
set. Now, instead of drawing in three blocks above the 1925
division on the horizontal line, he counts up three divisions and
makes a dot. Then above the 1926 division he counts up 5
Fig. 8
spaces, above 1927 six spaces and so on. When dots have been
placed for each year, he connects these with lines and he has
a full-fledged graph (see Fig. 8) of the kind that Radio-Tricians
and Radio engineers continually use in their work.
The dots can be connected by straight lines or by curved
lines-Radio-Tricians prefer curved lines to show that changes
are gradual rather than abrupt.
The specially ruled paper which is commonly used in making
drawings showing comparative values is "graph paper" and
is obtainable at any stationer's.
