Task Answer the review questions on the next slide on your own paper

Check your understanding 1.Which type of experiment might have low ecological validity? 2.What type of experiment is less likely to suffer demand characteristics? 3.What is a definition of quantitative data? 4.Which type of experiment might raise ethical issues? 5.Why is control of EVs important in an experiment? 6.How is an aim different to a hypothesis? 7.Why do psychologists need to write 2 hypotheses? 8.What is a null hypothesis? 9.In what situation would a non-directional hypothesis be used? 10.What does ‘operationalise’ mean? 11.Why do psychologists need to operationalise variables? 12.How could psychologists operationalise the variable ‘healthy eating’?

Homework questions – check your answers with a partner For each of the two studies answer the following questions: 1. Identify the IV and DV. 2. How could the IV and DV be operationalised? 3. Identify one possible extraneous variable. 4. In what way is this study high or low in validity? 5. Identify at least two possible ethical issues. 6. Describe how you would deal with each ethical issue.

Experimental design This refers to how Pts are put into the conditions in the IV

Experimental design – students often get confused Experimental design Repeated measures Independent groups Matched pairs Type of experiment LaboratoryFieldNatural

Task Look at the slides and fill in the table on experimental design in your booklets

Experimental design – how Ps are allocated to each condition of the IV Repeated measures Independent measures Matched participants

Independent Measures Recruit a group of participants Divide them into two This group does the experimental task with the IV set for condition 1 This group does the experimental task with the IV set for condition 2 Measure the DV for each group Compare the results for the two groups

Repeated Measures Recruit a group of participants Condition 1Condition 2 The group does the experimental task with the IV set for condition 1 The group repeats the experimental task with the IV set for condition 2 Compare the results for the two conditions

Matched Participants Recruit a group of participants Find out what sorts of people you have in the group Recruit another group that matches them one for one Condition 1Condition 2 Compare the results for the matched pairs Treat the experiment as independent measures

Independent Measures Advantages No order effects Fewer demand characteristics Same materials can be used with each condition Disadvantages Participant variables – extraneous variable? More participants required

Repeated Measures Advantages Participant variables are controlled Fewer participants required Disadvantages Order effects (practice, boredom) Demand characteristics Different materials must be used in each condition

Matched Participants Advantages Participant variables are controlled No order effects Fewer demand characteristics Same materials can be used Disadvantages Perfect matching is not possible Time consuming to match Ps More participants needed

Match the key term to the definition in your key terms Key term Participant VariablesParticipant Variables Order effectsOrder effects CounterbalancingCounterbalancing Definition An EV that occurs in a repeated measured design – Ps either get bored or get better through practice so performance changes An experimental technique used to overcome order effects – half Ps are tested in one condition first and half the other first, e.g. ABBA A type of EV in which any characteristic of individual participants may affect results (in independent measures design)

Homework Make own set of revision notes on everything studied so far (weeks 1 - 4)