Cognition lab

How to write a lab report

Purpose:

The purpose of a lab report is to report an experiment completely, from the motivation to the conclusions. Explain what question the experiment was intended to answer, what exact methodology was used, what the results of the experiment were, and what conclusions can be drawn from these results. Be as concise as possible, but assume that the reader knows nothing about what was done or why.

Format:

1. Abstract

One paragraph concisely summarizing the lab report. Why we did it, what we did, how it came out, and what it means.

2. Motivation ("Why did we do this experiment?")

You begin by explaining what question the experiment was designed to answer. Place the experiment in a theoretical setting: what issues about why systems are we trying to shed light on? After setting up the background in a more abstract way, focus on the specific issue being addresssed by this experiment. What is the hypothesis? What is the null hypothesis?

3. Method ("What did we do?")

Here we lay out and explain the design of the experiment. How were the general ideas operationalized into a concrete procedure? Exactly what procedure was carried out? What are the independent and dependent variables?

The general idea is to include enough detail so that someone else could carry out substantially the same experiment just by reading your lab report. The most important thing is to make sure you
explain exactly why the procedure was designed the way it was. Hence in describing the procedure, it is not enough to just repeat the description in the handout, which lays out the design but doesn't explicitly spell out the reasoning behind it. Never leave the reader thinking ``Why did they do that?''.

Depending on the experiment, this section is often divided into separate subsections, such as:

(a) Subjects. Simply describe the subjects of the experiment. For example: "Subjects were 27 members of a psychology class".

(b) Materials. Traditionally here you specify the devices and equipment that were used. In a psychology experiment it would be more typical to specify exactly how the lists of stimuli were constructed and selected. What kind of items were included in the list of stimuli, and in what numbers? In what order were they presented (e.g., random)?

(c) Procedure. Here is where you explain exactly what was done to the subjects using the materials. What was the subject's task? Here it is especially important to spell out exactly any counterbalancing schemes that were used. If there were different tasks, what order were the tasks performed in, and why?

4. Results ("What happened?")

This section presents the results of the experiment described in the previous section. Include graphs, and statistics, as appropriate—whatever is most informative. Can we reject the null hypothesis?

5. Discussion (``What does it mean?'')

This section interprets the results and draws conclusions. How do the results bear on the original hypothesis? In hindsight, were there any confounds or other methodological problems that might either account for the effect that was found, or account for why no effect was found?