Lesson 2

Recap  Hypotheses  IV and DV  What if something other than the IV affects the DV?  Why is this a problem?

Extraneous and confounding variables  Extraneous – controlled in a study  If they are not controlled they can be confounding variables  Confounding – variables that may have caused the results other than what was manipulated ---- > An experiment that fails to take a confounding variable into account is said to have poor internal validity.  Confounds the results in such a way that you are no longer measuring the effect of IV on the DV  Extraneous variable need to be controlled or variables that are not able to be controlled (e.g. Mood!)  These can be divided up into two types – Situational and participant variables

Extraneous Variables 1. Identify the IV and DV 2. Operationalise variables 3. Identify EV 1. A psychologist wants to investigate whether students who complete their 4 hours of independent study per week do better in the psychology exam than those students who only complete 1 hour per week An experiment to see if recall on a memory test is affected by time of day 3. Does drinking coffee whilst revising improve exam results? 4. An experiment to investigate the effects of fatigue on reaction time

Situational participant variables  Examples  Lighting, noise, temperature, time of day, disturbances  These should all be controlled or eliminated if possible  WHY is this important in an experiment?  Controlling extraneous variables means they are held constant for all participants so that the variables affect everyone equally.

Participant Variables  How can participants affect the results of a study?  Motivation, personality, background, personality, intelligence, gender, age etc.  What is easier to control? Why?  Controlling variables:  Controlling variables: Only necessary if those variables might have an unwanted impact on the DV.  Example?

List some situation and participant variables for the following examples. How you would control/eliminate them?  An investigation into sporting experience and the ability to shoot a hole in one with a basketball  An investigation to see if rehearsal was a better memory technique to learn a list of digits than creating a mental picture of the digits Worksheet:

Laboratory experiments - practice  Plan a laboratory experiment:  based on this theory: ‘different levels of praise affects the time children spend washing dishes.’  Aim?  Hypotheses  Experimental  Null  Directional? Non-Directional?  What type of setting should this take place in? Why?  What will your IV and DV be? Which variable is manipulated?  Which variables are controlled in laboratory experiment?  Participant and situation variables – examples?  What is the aim of a lab experiment?  Define cause and effect  To find a cause and effect conclusions

Experimental research designs  How are the participants sorted into groups to study them? 1. Independent groups design? 2. Repeated measures? 3. Matched pairs?

H/W Strengths and weaknesses of research designs Independent groupsRepeated measuresMatched pairs Definition Strength Weakness

Strengths and weaknesses of research designs Independent groupsRepeated measuresMatched pairs Definition Strength Weakness

Practical tip!  When carrying out an experiment with repeated measures design, make sure you use counterbalancing or using randomisation when allocating conditions to participants  Counterbalancing: Counterbalancing is a method of controlling for order effects in a repeated measure design by either including all orders of treatment or randomly determining the order for each subject.  E.g. one participants takes part in 1 st condition first then second participants takes part in 2 nd condition 1 st – there fore order effects may even out.  Randomisation: Order is randomised. I.e. there are 2 conditions and a coin is tossed to see which condition the participant takes part in first. Should cancel out order effects.

H/W Compare lab experiments with field experiments using strengths and weaknesses. (12 marks)