ERA with no control group?

[yien_quek]

So, for my 2nd SAC, we've done an experiment on perceptual set and will be doing an in-class ERA when school reopens. However, for the experiment, each class was split into 2 groups, and both groups were exposed to the independent variable, thus no control group.

If that's the case, then how would one write an ERA for this experiment? Specifically, the operational hypothesis, the experimental design, and any possible problems that may have risen from using 2 experimental groups.

Though both groups were exposed to the independent variable, the IV for both groups were sort of different. An example (not what we did, but similar) would be that group 1 was exposed to the animals and then shown the ambiguous figure, and group 2 was exposed to the faces of the people, and then shown the ambiguous figure.

Then would the purpose of the experiment be comparing the probability of interpreting the final ambiguous image consistent with the previous images that the participant was exposed to? e.g. see animals, interpret as animal. see people, interpret as person.

Using Bugelski and Alampay's experiment as an example, would an operational hypothesis of an experiment with no control group be something like:
"it was hypothesized that vce 3/4 psychology students from blahblah high school who were exposed to 4 images of animals would be more likely to interpret an ambiguous image as a rat as opposed to those who were exposed to 4 images of people who would be more likely to interpret the same ambiguous image as a man - operationalized as the number of people who consistently saw the ambiguous image as an animal or as a person."
would that be okay?

experimental design: independent groups? since the definition does not exclusively state that the groups participants are allocated to has to be a control and an experimental group...

problems with no control? if the purpose is consistency, then would a control be necessary at all?
maybe a problem would be the ambiguity of the ambiguous image? like the rat/man image looked more like a rat when i first saw it w/o any previous images.

[Glockmeister]

Remember, regardless of what sort allocation you're using, hypothesises have the same structure.

- The population
- The IV
- The DV
- A direction

So in that case, you population is VCE 3/4 Psych students, your IV is exposure to animals or people and the DV would be interpretation of the ambiguous figure. Also, it's possible to have two hypothesises in the one study and I would argue that you'll need to do that here.

Your example sounds to me like a independent groups, and your right, it doesn't have to be an experimental and control groups. All you need is a number of what uni psych textbooks call 'treatment' groups and that everyone would only be exposed to one such group. The lack of control may make the study a bad study, but it doesn't change what sort of study it is.

I would argue that there is a need for a control, you might need someone who isn't exposed to an image of the animals or a person to establish a baseline, because you can't assume that 50% of the population would interpret the image as a man and 50% rat (when not exposed to an image at all). It could be that, if say the hypotheses is shown to be right(remember, never proven), it could be the fact that the image has been designed in such a way that it is 'stacked' against seeing it as a rat. Generalising this problem further to studies such as these, independent groups design in general will always have this sort of flaw, because 'individual differences' in the people within groups may effect the experiment. If you could remember that last point, you will be well on your way to being able to easily answer questions like this on the exam/SACs that you do.

Hope that helps.

[yien_quek]

hey, yeah! that helped heaped! thanks alot!

but just a question. As i know it, a hypothesis is supposed to compare 2 things, the presence of the IV, and the absence of the IV.

for example: it was hypothesized that (population) who drank milo before playing soccer would score more points in the soccer game than those who did not drink milo.
presence of IV: drink milo
absence of IV: didn't drink milo

so in my case, like you said, the IV would be the exposure to the animals or people. so what would be the absence of the IV? no exposure at all?

or would you do something else, something like: it was hypothesized that (population) who were presented with images of animals would interpret the final ambiguous figure as being a 'rat', and participants in another group that were presented with images of people would interpret the final ambiguous figure as being a 'man'

EDIT:
also, as there is no control group, would you still be able to say the hypothesis was supported?
or would you just classify that as a flaw in the experiment?

[bomb]

Ok, for your animals/people experiment (I'm assuming it is for perceptual sets/context) you have two conditions right?

That's what you need to include in your hypothesis. Two conditions.

This could be experimental/control or whatever, but in this case, it is not.

So,

Hypothesis: It is hypothesized that the context in which an ambiguous image is displayed will influence the participants perception of the figure. If the image is displayed after a series of animals, it will be percieved as a rat, if the image is displayed after a series of human faces, it will be percieved as the face of a man.

IV: Context in which the stimulus is presented. Either in a series of animals or human faces.

DV: Participants perception of the stimulus.

And yes, you can say the hypothesis was supported (see the hypothesis above) if you use that hypothesis.

P.S. Milo sucks.

[yien_quek]

yeah, thanks!! that certainly clears things up.

however, it's perceptual set/past experience. well, at least i think it's past experience.
i've seen websites that say that the bugelski and alampay experiment is based on context, but the Grivas Psych 3/4 textbook lists it as past experience.

nonetheless, your post cleared up my hypothesis question, thanks again!

P.S. Milo is awesome.

[bomb]

Yup, you're right, past experience =] (In the book)

Glad I could help.

[Glockmeister]

yeah, thanks!! that certainly clears things up.

however, it's perceptual set/past experience. well, at least i think it's past experience.
i've seen websites that say that the bugelski and alampay experiment is based on context, but the Grivas Psych 3/4 textbook lists it as past experience.

nonetheless, your post cleared up my hypothesis question, thanks again!

P.S. Milo is awesome.

What bomb has said looks good to me (although you must have the population in the hypothesis, this is very important)