The first thing our students did on their introduction to research methods course was to complete a word search puzzle similar to that shown above. Each student did the puzzle on a computer and when they had found all the words, the time it took them to complete the puzzle (in seconds) appeared on the screen.
Now what the students didn't realize at the time is that they were actually taking part in an experiment.
I (along with my teaching support team) took half the students into one room PC lab 1. My colleague Dr Tyfa (along with his teaching support team) took the other half of the students into another room PC lab 2.
When the students were doing the puzzle in PC lab 1 (my lab), the teaching team made their presence felt as much as possible, walking up and down each bank of computers, looking over the students shoulder, essentially being as conspicuous as possible.
In PC lab 2 (Dr Tyfa's lab) the teaching team did the opposite i.e. they remained as inconspicuous as possible and showed no interest in what the students were doing at all.
The students were completely unaware what was going on, as far as they were concerned the object of the exercise was to simply collect some data i.e. the time taken to complete the puzzle, which they could then practice entering into a statistical software package.
The true nature of the exercise wasn't revealed until the following week when I gave a lecture on the experimental method. Because what I was able to do now was introduce each key experimental design concept in turn and apply it something the students had direct experience of i.e. the word search puzzle experiment.
(Photo Credit: Athary)
Before you move on, take a look at the quick reference guide I put together which covers the experimental design concepts addressed in the lecture. Better still; print out this page and the next so you can refer to the quick reference guide to it as you continue the tutorial.
EXPERIMENTAL HYPOTHESIS (H1)The prediction of the outcome of the experiment
ONE-TAILED EXPERIMENTAL HYPOTHESIS
Predicts the way that behavior will change
TWO-TAILED EXPERIMENTAL HYPOTHESIS
Simply states that the behavior will change
NULL HYPOTHESIS (H0)
Simply states that any observed differences between groups were down to chance.
INDEPENDENT VARIABLE (IV)
The one factor that is different between the conditions
DEPENDENT VARIABLE (DV)
The aspect of behavior that is measured
EXTRANEOUS VARIABLE
Anything, other than the IV that might have had an effect on the result of the experiment.
CONFOUNDING VARIABLE
An extraneous variable that does effect the result of the experiment. In doing so, it becomes impossible to say whether any difference found was due to the IV or the confounding variable.
INDEPENDENT SUBJECTS DESIGNSome subjects perform in experimental condition and others in control condition.
REPEATED MEASURES DESIGN
All subjects perform in both experimental condition and control condition
MATCHED PAIRS DESIGN
As a result of a pre-test subjects are sorted into pairs. One of the pair performs in the experimental condition and the other performs in the control.
ORDER EFFECTS
If a participant has to perform a series of actions, the order in which she/he performs them will have an effect on the efficiency of each action. The two main order effects are practice (increases efficiency) and fatigue (decreases efficiency).
COUNTERBALANCINGEmployed to ensure that order effects have an equal effect by alternating the conditions.
Now imagine trying to understand these concepts without a point a reference. Thankfully you don't have to and I hope that by providing you with the same point of reference as my students, you'll see that as we examine these key concepts that they aren't that difficult to get your head around and actually make a great deal of sense.
The first thing we need to do, however, is to understand the logic of the experimental method. Namely that:" If two groups of participants are equal in all respects save one and are not similar in respect of a behavior that is being measured, then the difference between them must be attributable to the one way in which they were different." (J.S Mill)
Hopefully by exploring this logic in relation to the word search experiment you'll see that it’s actually very straightforward.
When we ran the experiment we had two groups of participants, i.e. some in (PC lab 1) and some in (PC lab 2). Now for the time being, let’s accept that these two groups of participants were equal in all respects save one. This of course begs the question, what was the one way in which the two groups of participants were not equal?
When the students were doing the puzzle in PC lab 1 (my lab), the teaching team made their presence felt as much as possible, walking up and down each bank of computers, looking over the students shoulder, essentially being as conspicuous as possible.
In PC lab 2 (colleagues lab) the teaching team did the opposite i.e. they remained as inconspicuous as possible i.e. showed no interest in what the students were doing at all.
Now if it transpired that the psychology students in PC lab 1 and PC lab 2 were not similar in respect of the behavior that was being measured (In our case the time taken to complete a word search puzzle), then according to the logic of the experimental method, this difference must be attributable to level of teacher presence. In other words
Level of teacher presence (the cause) made a difference in the time taken to complete the puzzle (the effect).So the first thing to note about the experimental method is that it is fundamentally concerned with establishing cause and effect.