Programming Stata - Agricultural Statistical Data Analysis Using Stata - page 143

The next line calculates the coefficient of variation (CV), which is
usually the standard deviation divided by the mean, which is multi-
plied by 100 and reported as a percent. In this case, using the root
MSE divided by the mean of the dependent variable and multi-
plied by 100 results in a similar value. The CV gives a unit indepen-
dent value of the dispersion around the mean. In the context of an
experiment, a smaller value is considered better and often indicates
the overall experimental conditions or model fit. This value also can
change based on the type of experiment or crop involved. Because
this value is not reported in any particular unit (e.g., inches, pounds,
lbs/acre, etc.), it can be used to compare the performance of different
experiments with different units of measure. It is possible under some
circumstances to have a CV that is over 100%. This can indicate a
problem with the experiment or the nature of the collected data. In
any event, values over 100% indicate that the means are of little value.
The next two lines display the output for this program. The dis-
play command displays what follows in the Results window and
using display as is followed by a style that is determined by the
color scheme set in the Preferences. The styles available are text,
result, error, and input . he text style is used for identi-
fying text. The results style is for the results of calculations. The
error style is for displaying errors, and the input style is rarely
used, but is generally reserved for user input. The uses of these styles
are not set in stone, but rather are suggested uses for consistency across
commands. To best see the effects of styles, change the preferences to
the classic scheme and run this program.
The following lines within the program illustrate the use of these
styles.
display as text “Coefficient of Variation:
“ as result%-2.0f `cv' “%”
display as text “Fisher's Protected LSD (p≤0.05):
“ as result%-8.4f `z'
he % -2.0f and % -8.4f are formatting directives. The % indi-
cates what follows is for formatting. The - indicates it should be left
justified. The number to the left of the decimal is the total output
width and the number to the right of the decimal is the number of
decimal places. The f indicates that it is a fixed format in terms of the