TaskTask

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

Check your understandingCheck your understanding1.1. Which type of experiment might have low ecological validity?Which type of experiment might have low ecological validity?

2.2. What type of experiment is less likely to suffer demand What type of experiment is less likely to suffer demand characteristics?characteristics?

3.3. What is a definition of quantitative data?What is a definition of quantitative data?

4.4. Which type of experiment might raise ethical issues?Which type of experiment might raise ethical issues?

5.5. Why is control of EVs important in an experiment?Why is control of EVs important in an experiment?

6.6. How is an aim different to a hypothesis?How is an aim different to a hypothesis?

7.7. Why do psychologists need to write 2 hypotheses?Why do psychologists need to write 2 hypotheses?

8.8. What is a null hypothesis?What is a null hypothesis?

9.9. In what situation would a non-directional hypothesis be used?In what situation would a non-directional hypothesis be used?

10.10. What does ‘operationalise’ mean?What does ‘operationalise’ mean?

11.11. Why do psychologists need to operationalise variables?Why do psychologists need to operationalise variables?

12.12. How could psychologists operationalise the variable ‘healthy How could psychologists operationalise the variable ‘healthy eating’?eating’?

Homework questions – check Homework questions – check your answers with a partneryour 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 designExperimental design

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

Experimental design – students Experimental design – students often get confusedoften get confused

Experimental designExperimental design

Repeated measuresRepeated measures

Independent groupsIndependent groups

Matched pairsMatched pairs

Type of experimentType of experiment

LaboratoryLaboratory

FieldField

NaturalNatural

TaskTask

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

Experimental design – how Ps Experimental design – how Ps are allocated to each condition are allocated to each condition

of the IVof the IV

RRepeated measuresepeated measures

IIndependent measuresndependent measures

MMatched participantsatched participants

Independent MeasuresIndependent MeasuresRecruit a group of

participantsDivide 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 MeasuresRepeated MeasuresRecruit a group of

participants

Condition 1 Condition 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 ParticipantsMatched ParticipantsRecruit 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 1 Condition 2

Compare the results for the matched pairs

Treat the experiment as independent

measures

Independent MeasuresIndependent Measures

AdvantagesAdvantages

No order effectsNo order effects

Fewer demand Fewer demand characteristicscharacteristics

Same materials can be Same materials can be used with each used with each conditioncondition

DisadvantagesDisadvantages

Participant variables – Participant variables – extraneous variable?extraneous variable?

More participants More participants requiredrequired

Repeated MeasuresRepeated Measures

AdvantagesAdvantages

Participant variables Participant variables are controlledare controlled

Fewer participants Fewer participants requiredrequired

DisadvantagesDisadvantages

Order effects Order effects (practice, boredom)(practice, boredom)

Demand Demand characteristicscharacteristics

Different materials Different materials must be used in each must be used in each conditioncondition

Matched ParticipantsMatched Participants

AdvantagesAdvantages

Participant variables Participant variables are controlledare controlled

No order effectsNo order effects

Fewer demand Fewer demand characteristicscharacteristics

Same materials can Same materials can be usedbe used

DisadvantagesDisadvantages

Perfect matching is Perfect matching is not possiblenot possible

Time consuming to Time consuming to match Psmatch Ps

More participants More participants neededneeded

Match the key term to the Match the key term to the definition in your key termsdefinition in your key terms

Key termKey term

• Participant VariablesParticipant Variables

• Order effectsOrder effects

• CounterbalancingCounterbalancing

DefinitionDefinition

An EV that occurs in a repeated An EV that occurs in a repeated measured design – Ps either get measured design – Ps either get bored or get better through bored or get better through practice so performance changespractice so performance changes

An experimental technique used to An experimental technique used to overcome order effects – half Ps overcome order effects – half Ps are tested in one condition first are tested in one condition first and half the other first, e.g. ABBAand half the other first, e.g. ABBA

A type of EV in which any A type of EV in which any characteristic of individual characteristic of individual participants may affect results (in participants may affect results (in independent measures design)independent measures design)

HomeworkHomework

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