Producing Lab Reports of
by Zoya PopoviŠ and Edward Kuester
Over the years, we have found that there are several very common mistakes
made in student lab reports. These guidelines are intended to help you
present your data in a more professional manner and also make your lab
reports easier for the TAs to grade. Here we list many of the more common
mistakes made in the writing of lab reports (and other technical literature
as well). Remember this guiding principle: even though you as an engineer
may understand thoroughly what you have done, this is of no practical value
unless you can communicate that knowledge to others. Imagine that you are
writing your report for a technically literate person who does not know
what you did or why.
A first major error is that many graphs do not present data effectively.
In order to make an effective graph, you should follow some standard conventions:
Use either linear or log scales on both x and y axes. Many
students used arbitrary scales or simple labelled their data points on
the x and y axes. Standard scales make it easier to interpret
a graph. Nonstandard scales make data hard to decipher.
Make your graphs at least 7.5 cm (three inches) tall and 10cm (four inches)
wide to ensure clarity. Smaller graphs hide smaller variations in the data;
computer-generated graphs are great but not necessary.
Label all axes and traces. Also, do not put more than two traces on a graph
unless you are trying to show a progression of data.
If there are two traces or more on a graph, use different marks for the
data points; i.e. x's for trace one, o's for trace two, etc. Use two or
more colors for the traces if practical.
% error = 100 (Value obtained - Value expected) / (Value expected)
That's it. If you follow these recommendations, your instructors
will be happier, you will not lose points because of your report style,
and, most importantly, you will be a better engineer.
Another weakness in lab reports is the style of tables used. Use a
vertical table (an independent variable column next to the dependent variable
columns) whenever you have the numerical data available. Please do not
use horizontal tables; they are very hard to read and thus do not present
your data effectively. Use your ruler to organize your tables and make
them easier to read.
Writing: "...the measurements agree pretty well with the expected values..."
does not mean a thing. It is important to do good error analysis. Usually,
this should be done by calculating percent error: