PSYA1: Cognitive Psychology Memory “Experimental Design”

Experimental Design Define Experimental Design Outline the difference between a control and experimental condition Define independent groups, repeated measures and matched pairs Give at least one elaborated strength and weakness of each. Outline what is meant by order effects. Outline how order effects could be counterbalanced. Complete sheet (HW)

How will I know if I am learning? By the end of the lesson… Success Criteria How will I know if I am learning? By the end of the lesson… E Will be able to define key methodology terms. C Will be able to describe the different types of experiment. A Will be able to explain the advantages and disadvantages of each type of experimental design.

To Start.. • Identify the IV and the DV • Identify the two or more conditions in the experiment, highlighting which condition is the control (if there is one) A) A researcher is interested in whether alcohol has an effect on memory. One group of participants are given a list of words to learn and then given an alcoholic drink. The other group is given the same list of words, and a glass of water. The number of words they can remember is recorded. IV- Alcohol DV: Memory (the number of words participants can remember – operationalised) Experimental group= list of words and alcoholic drink Control group= list of words and water

What is meant by experimental design? If you have decided that an experiment is the best approach to testing your hypothesis, then you need to design the experiment. Experimental design refers to how participants are allocated to the different conditions (or IV groups) in an experiment.

Experiments Recap What is an IV? _________ What is a DV? _________ In an experiment, you can have two conditions: The experimental condition is where you manipulate a variable to see the effect. The control condition is where nothing is manipulated so that we have a base line to compare our results with.  

Come up with your own research experiment. What is your IV and DV? Experiments Come up with your own research experiment. What is your IV and DV?

What do we mean by experimental design? Experimental design refers to how we use our participants in our experiment. There are three main ways that participants can be used. Independent measures Repeated measures Matched pairs

Independent Groups Experiments Condition A Condition B There are two separate groups of participants. One group takes part in condition A, the other takes part in condition B.

Independent Group design: Different participants are used in each condition of the independent variable. This means that each condition of the experiment includes a different group of participants. This should be done by random allocation, which ensures that each participant has an equal chance of being assigned to one group or the other. Independent measures involves using two separate groups of participants; one in each condition. Independent Group design:

Repeated Groups Experiments Condition A Condition B There is only one group of participants. This group takes part in both conditions.

REPEATED MEASURES GROUP DESIGN The same participants take part in each condition of the independent variable. This means that each condition of the experiment includes the same group of participants.

Matched Pairs Experiments Condition A Condition B There are two separate groups, but this time they are matched into pairs for certain qualities, such as age or intelligence. One of each pair takes part in condition A, the other takes part in condition B.

Do Sheet: Which Experimental Design? Experiments Do Sheet: Which Experimental Design? Do Independently and in Silence. If you need help, put your hand up and ask the teacher only.

Choose the participant design most suitable for your own experiment. Experiments Choose the participant design most suitable for your own experiment.

Can you think of any problems with the participant designs? Experiments Order Effects Can you think of any problems with the participant designs?

Order Effects Experiments Order effects occur in repeated groups design, when all participants take place in all the experimental conditions. Practice effects might occur. After they have done the first condition they may be well practised to complete the second condition. They also may become tired after the first condition and fatigue may affect their performance on the second condition. The solution = counterbalancing and randomisation. Counterbalancing. E.g. half of the participants participate in condition A before condition B and vice versa. This means that the first and second condition is not the same for every participant. Randomisation. Participants are assigned to condition A or B first by tossing a coin or picking out a name.

Advantages and disadvantages of independent group design Avoids order effects (such as practice or fatigue) as people participate in one condition only. If a person is involved in several conditions they man become bored, tired and fed up by the time they come to the second condition, or becoming wise to the requirements of the experiment! DISADVANTAGES: More people are needed than with the repeated measures design (i.e. more time consuming) Differences between participants in the groups may affect results, for example; variations in age, sex or social background. These differences are known as participant variables (i.e. a type of extraneous variable).

Advantages and disadvantages of repeated group design Fewer people are needed as they take part in all conditions (i.e. saves time) Disadvantages: There may be order effects. Order effects refer to the order of the conditions having an effect on the participants’ behaviour. Performance in the second condition may be better because the participants know what to do (i.e. practice effect). Or there performance might be worse in the second condition because they are tired (i.e. fatigue effect).

Counterbalancing Counterbalancing: Suppose we used a repeated measures design in which all of the participants first learned words in loud noise and then learned it in no noise. We would expect the participants to show better learning in no noise simply because of order effects. To combat order affects the research counter balances the order of the conditions for the participants. Alternating the order in which participants perform in different conditions of an experiment. The sample is split in two groups experimental (A) and control (B). For example, group 1 does ‘A’ then ‘B’, group 2 does ‘B’ then ‘A’ this is to eliminate order effects. Although order effects occur for each participant, because they occur equally in both groups, they balance each other out in the results.

Advantages and disadvantages of matched pairs Reduces participant (i.e. extraneous) variables because the researcher has tired to pair up the participants so that each condition has people with similar abilities and characteristics. Avoids order effects, and so counterbalancing is not necessary. DISADVANTAGES: Very time-consuming trying to find closely matched pairs. Impossible to match people exactly, unless identical twins!

Experiments What would be the advantages and disadvantages of the participant design in the context of your own experiments?

How would you design an experiment Experiments To Finish You want to investigate gender differences in the speed of texting on mobile phones in order to see who are the fastest, males or females. How would you design an experiment to test this? -What is the IV and DV? -What participant design would you use (repeated/independent/matched pairs)? -How would you design the experiment?