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.

• Graphs

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.

• Tables

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.
 
• Error Analysis

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:

The only exception to this is if the expected (theoretical) value is close to zero, so that the percent error goes to infinity. In such cases, use the absolute error:

                                error =  Value obtained - Value expected
 

• Calculations

This should not be anything new, but we do expect you to show a certain amount of your work, including equations. It is a good habit at the very least. Also, if you show your work, we can tell you where you make your mistakes.
 
• Completeness

Any significant step in the lab should be described in the lab report, even if a direct question is not asked about that step. Remember that if you do not write it down, you will not get credit for it. Be as concise and clear as possible. Perhaps it is the result of late night caffeine binges, but some answers that we have seen are quite muddled. Do not forget that "beating around the bush" and unclear answers will NEVER help your grade.  Use The Elements of Style by Strunk and White, if you need to improve your writing.