Psychological Research method EXPERIMENTS Psychological Research method

Key Terms – Experiments Please complete these definitions on your worksheet as you go Ethics Informed consent Right to withdraw Independent Measures Repeated Measures Matched-Pairs Counter Balancing Operationalising Hypothesis Alternative Hypothesis Null Hypothesis descriptive statistics (mean, median, mode, range) bar chart Laboratory Experiment Field Experiment Quasi Experiment Independent Variable Dependent Variable Control of variables Confounding Variable Extraneous Variable Replication Cause and Effect Ecological Validity Demand Characteristics

Experiments Three types of experiments: Laboratory experiments Highly controlled / artificial Field experiments Controlled variables in a natural environment Quasi (natural) experiments We have no control over the independent variable – it’s ‘naturally’ occurring (eg Gender)

Experiments Independent Dependent Variable Variable (IV) ~ the variable we manipulate / change Dependent Variable (DV) ~ the variable that we measure Extraneous Variable: a variable that could affect the DV but has been controlled for so it doesn’t. Confounding Variable: a variable that effects the DV

Experiments Single Blind – Double Blind – Control Groups Extraneous Variables Participant Variables Independent Measures = Individual Differences Situational Variables Any feature of the experiment that could influence a participants behaviour Single Blind – Double Blind – Control Groups

Experiments – Hypotheses How are we measuring memory? What’s better or worse? Higher / Lower? More / Less? Participants memory will be much worse when there is a distraction in the room than when there is no distraction. Participants memory will be much worse when there is a distraction in the room than when there is no distraction. What is the distraction? How are we manipulating it? Operationalising your hypothesis How have you manipulated your IV? How have you measured your DV?

Experiments – Hypotheses Participants memory will be much worse when there is a distraction in the room than when there is no distraction. Participants will remember significantly more words from a list of 20 presented for 60 seconds when they are in a room with no distractions than participants who are in a room where rock music is playing in the background.

Experiments – Hypotheses Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. There will be no significant difference between participants who [do something] and those who [do something else]. Any difference will be down to chance. Alternative Null

Experiments – Hypotheses Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. There will be a significant difference between participants who [do something] and those who [do something else]. 1Tailed 2Tailed

Sampling General Population Representative Sample Generalisations Sampling Techniques Sample

Sampling Opportunity Sample People who are there at the time. Quick / Cheap / Easy Not representative Random Sample Each person in the GP has an equal chance of being chosen. Expensive and time consuming. Representative sample

Sampling Self-Selected Participants volunteer to be in the sample following advert etc. Quick / Cheap / Easy Not representative What kind of person volunteers for a psychology experiment? Snowball Sampling One person tells others who tell others … Allows us to collect difficult to locate people Time consuming

Experiments Repeated Measures Independent Measures Participants are only in one condition. Repeated Measures The same participants repeat the two conditions Condition 1 Condition 2 Condition 1 Condition 2 Counter balancing – alter order of Pp’s

Experiments Matched Pairs – make two groups of participants as similar as possible. Condition 1 Condition 2 Male (Bob) 21 IQ = 105 Male (Richard) 21 IQ = 105 Female (Dawn) 25 IQ = 115 Female (Cara) 25 IQ = 115

Strength Weakness Independent Measures Repeated Measures Matched Pairs No Order Effects Fewer Demand Characteristics Individual Differences Repeated Measures No Individual Differences Order Effects (counter balancing) Matched Pairs Controls for Individual Differences Can be difficult and costly. Evaluation of Experimental Designs

Ethics Debriefing Deception – can not! Right to Withdraw Informed Consent Protection from physical and psychological harm Additional considerations: Confidentiality Observation Advice Colleagues

Scattergram to show the Correlation between variable Data Analysis Scattergram to show the Correlation between variable 1 and variable 2 Titles are VERY important. Title your axis, the integers and give the graph a title.

Data Analysis Descriptive Statistics Summary of data to illustrate patterns and relationships – BUT can’t infer conclusions Inferential Statistics Statistical tests that allow us to make conclusions in relation to our hypothesis. eg. Mann-Whitney or Spearman’s Rho.

Ethics Cause & Effect Types of Experiments Sampling Methods Independent & Dependent Variables Confounding & Extraneous Variables Cause & Effect Types of Experiments Laboratory Field Quasi (natural) Experimental Methods Independent Measures Repeated Measures Matched-Pairs Sampling Methods Opportunity Random Snowball Stratified Self-Selected Ethics Ecological Validity Reliability Validity