Tables

Data tables are the core of lab reports: without data, there is no report to submit. This chapter goes over the basic guidelines for creating efficient data tables.

Each table should be numbered, and have a title. Each column of a table should be headed with the proper dimension and unit. Identify measured and calculated values.

Consider an experiment where a student measured the position of an object at set times. The purpose of the experiment is to determine the velocity and acceleration of the object as functions of time. The student collected the following data: positions = 0.0 ± 0.5 mm, 12.5 ± 0.5 mm, 56.5 ± 0.5 mm, 128.7 ± 0.5 mm, and 265.2 ± 0.5 mm at times = 0.00 s, 0.20 s, 0.40 s, 0.60 s, and 0.80 s respectively. Assume that the times have no uncertainties for this experiment. You probably noticed that it is difficult to make sense of the data as written. A better way to represent the data is in a table as follows.

As simple as it looks, there are several elements to this table that must be clearly pointed out. First, and most importantly, the table itself is labeled and has a title; the table is useless without a meaningful title. Table labels are also important as they allow you to clearly refer to your data from other sections of your lab report. Second, since Table 1 (note the reference) is small it does not need to take up the entire width of the page.

Table 1 has two other major features that need to be looked at: column labels and data entries. Each column label must clearly identify what physical quantity the data in the column represents. Notice that no data entry in any cell of the table has units written next to its numerical value. All data in a specific column of a table must share the same units of measure; the units of measure must also appear in the column label. As for the data entries themselves, no data entry in a given column has more precision than any other. Finally, all the positions have the same uncertainty. Instead of repeating that uncertainty for each data entry, it is allowed to place the uncertainty in the column label as part of the units of measure. However, this can only be done if the uncertainties for all data entries in the column are the same.

A few final comments about tables need to be made:

No data entry in a data set can have greater precision than any other entry in the same set. The individual cells of a data table must not be too large in comparison to the data they contain. For example, if each column in Table 1 were made half a page wide so that the table filled the whole width of the page, you would lose points in your lab report.

In labeling your columns or rows, avoid using scientific notation by using appropriate units. If you must use scientific notation, then you must use proper scientific notation like 1.03 x 10^–5 kg;

it is unacceptable—and you will be penalized—if you write 1.03E–5 kg, even if you use Microsoft Excel. Better yet, the appropriate power of 10 can be made part of the column or row label if it applies equally to all data entries in the set.

Finally, data tables must never be broken across pages or across margins of a page. To make a large data table fit on a single page, you may have to reduce the font size (but not lower than 10 pt), decrease the margin widths, or even play with the orientation of the print (landscape versus portrait). Whatever you do, the data table must remain legible. If you have too much data and it is impossible to fit your table on a single page, then do break it across pages but at the top of each page you must have the table's label and title as well as the column labels repeated.