Experimental methods
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This document provides an overview of experimental methodology in psychology. It discusses different types of experiments including laboratory, field, and quasi-experiments. It also covers key concepts like independent and dependent variables, as well as ethical issues and controls in experimental design."
![“[The studies] are often
brilliantly controlled and
scientifically
rigorous but
bear as much
resemblance to
[real life] as an Oxo
cube does to a cow.
Such studies can be
described as
impeccable trivia.”
Banyard and Grayson, 2008
Wednesday 12 February 2014
www.jamiesmind.co.uk
20](https://image.slidesharecdn.com/experimentalmethods-140212035755-phpapp02/85/Experimental-methods-20-320.jpg)
![Alternate
Participants who [do something] will be
significantly [faster/better/quicker etc] at
[something] than participants who [do
something else].
Null
Experiments – Hypotheses
There will be no significant difference
between participants who [do something]
and those who [do something else]. Any
difference will be down to chance.
Wednesday 12 February 2014
www.jamiesmind.co.uk
60](https://image.slidesharecdn.com/experimentalmethods-140212035755-phpapp02/85/Experimental-methods-60-320.jpg)
![Experiments – Hypotheses
1Tailed
Participants who [do something] will be
significantly [faster/better/quicker etc] at
[something] than participants who [do
something else].
2Tailed
There will be a significant difference
between participants who [do something]
and those who [do something else].
Wednesday 12 February 2014
www.jamiesmind.co.uk
61](https://image.slidesharecdn.com/experimentalmethods-140212035755-phpapp02/85/Experimental-methods-61-320.jpg)
Experimental methods
- 1. How science works EXPERIMENTAL METHODOLOGY Wednesday 12 February 2014 www.jamiesmind.co.uk 1
- 2. Can you test these? How? 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. You accidentally swallow about 8 spiders a year. You only use 10% of your brain. Men think about sex every seven seconds. There are more people than chickens in the world. The Great Wall of China is the only human-made object visible from the moon. Sneezing seven times in a row is the same as an orgasm. If you sneeze with your eyes open your eyes will pop out of your head. It is impossible to lick your elbow. Dogs and cats are colour-blind. Goldfish only have a 7 second memory. Wednesday 12 February 2014 www.jamiesmind.co.uk 2
- 3. Learning Objectives By the end of this lesson you: • Must be able identify and describe the different types of experimental methodology in Psychology. • Should be able to identify the idenpendent and dependent variables from an experimental aim. Wednesday 12 February 2014 www.jamiesmind.co.uk 3
- 4. Wednesday 12 February 2014 www.jamiesmind.co.uk 4
- 5. Types of Experiments • Laboratory experiments – Highly controlled / artificial situation – The experimenter has explicit control over the IV • Field experiments – Controlled variables in a natural environment • Quasi (natural*) experiments – No control over the independent variable and Pps cannot be randomly allocated to a condition. – it’s ‘naturally’ occurring (eg Gender) * Do not get this confused with a Field experiment! Wednesday 12 February 2014 www.jamiesmind.co.uk 5
- 6. Wednesday 12 February 2014 www.jamiesmind.co.uk 6
- 7. Research investigating if there is a difference between students who are deprived of sleep and students who have had plenty of sleep. Wednesday 12 February 2014 www.jamiesmind.co.uk 7
- 8. An experiment to investigate if men are more obedient than women when an experimenter asks them to inflict pain onto another person. Wednesday 12 February 2014 www.jamiesmind.co.uk 8
- 9. A study to investigate if people on a train travelling from Hull to York would help someone who falls over more if they were dressed as a disabled person or a drunk. Wednesday 12 February 2014 www.jamiesmind.co.uk 9
- 10. We want to investigate if a person will remember images or words better having been exposed to them for thirty seconds. Wednesday 12 February 2014 www.jamiesmind.co.uk 10
- 11. Will white rats be able to run a maze quicker than grey rats? Wednesday 12 February 2014 www.jamiesmind.co.uk 11
- 12. Experiments cause effect Independent Variable (IV) Dependent Variable (DV) Wednesday 12 February 2014 www.jamiesmind.co.uk 12
- 13. Task Based on the way the research questions are written complete the Independent Variable (IV) and Dependent Variable (DV) boxes only. You can work in pairs if you wish. Time: 10 minutes Wednesday 12 February 2014 www.jamiesmind.co.uk 13
- 14. Experiments cause effect Independent Variable (IV) Dependent Variable (DV) Confounding Variable: a variable that effects the DV Extraneous Variable: a variable that could affect the DV but has been controlled for so it doesn’t. Wednesday 12 February 2014 www.jamiesmind.co.uk 14
- 15. • independent variable: that variable that is being manipulated; the difference between the experimental conditions. • dependent variable: the variable that is being measured by the experimenter. • extraneous variable: a variable which could affect the dependent variable but which is controlled so that it does not become a confounding variable. • confounding variable: a variable which has an unintentional effect on the dependent variable. Wednesday 12 February 2014 www.jamiesmind.co.uk 15
- 16. Review Using your course reader (pg. 54-57) make a review sheet on the types of experiment. Ensuring you have notes on laboratory, field and quasi experiments. You can choose how you want to lay it out. Some ideas: •Mind map •Full notes •Tri-page fold –type-thing Wednesday 12 February 2014 www.jamiesmind.co.uk 16
- 17. Design your own … Choose 5 of the experiments from last lesson’s handout. For each of these consider: a)How would you design the experiment? What would the procedure be? b)What experiment type would you use and why? c)What experimental design would you use and why? d)What other measures would you use to control for confounding variables?
- 18. How science works EXPERIMENTAL METHODOLOGY Wednesday 12 February 2014 www.jamiesmind.co.uk 18
- 19. Learning Objectives By the end of this lesson you: • Must be able to list the ethical issues in psychological research. • Should be able to describe the different types of controls in psychological research. Wednesday 12 February 2014 www.jamiesmind.co.uk 19
- 20. “[The studies] are often brilliantly controlled and scientifically rigorous but bear as much resemblance to [real life] as an Oxo cube does to a cow. Such studies can be described as impeccable trivia.” Banyard and Grayson, 2008 Wednesday 12 February 2014 www.jamiesmind.co.uk 20
- 27. refe rs to arte an e fact xper whe form imen an in re pa ta l the rticip terp expe ants reta and rime tion unc nt's of onsc their purp ious ose beh acco ly ch avio ur rdin ang gly e
- 29. The experimenter The experimenter effect is a term used effect is a term used to describe subtle to describe subtle cues or signals from cues or signals from an experimenter an experimenter that affect the that affect the performance of performance of participants in participants in studies. studies. The cues may be unconscious nonverbal cues, The cues may be unconscious nonverbal cues, such as muscular tension or gestures. They such as muscular tension or gestures. They may be vocal cues, such as tone of voice. may be vocal cues, such as tone of voice.
- 31. Ethics Wednesday 12 February 2014 www.jamiesmind.co.uk 31
- 32. • • • • • Consent Deception Debriefing Withdrawal Confidentiality Wednesday 12 February 2014 • • • • Protection Observation Advice Colleagues www.jamiesmind.co.uk 32
- 33. Landis (1924) Participants required to behead a live rat with a butchers knife Johnson et al. (1939) Children deliberately pressured psychologically to induce stuttering resulting in lifelong emotional suffering Sheridan & King (1939) Participants required to administer electric shocks to puppies to such an extent that death occurred Willowbrook (1956) Children fed extracts of stool from individuals infected with hepatitis Wednesday 12 February 2014 www.jamiesmind.co.uk 33
- 34. The Ethics Love Affair How to remember the ethical guidelines A pair of consenting adults were deceiving their partners and having a love affair even after their colleagues had advised them not to. They had gone to the park to ‘make love’ so they debriefed but they didn’t have any protection so he had to withdraw. Some perv was observing and told everyone about it and their affair was confidential no more. Wednesday 12 February 2014 www.jamiesmind.co.uk 34
- 35. Task Some experimental Questions! You can use your personal notes or course reader. Time: 20 minutes Wednesday 12 February 2014 www.jamiesmind.co.uk 35
- 36. How science works EXPERIMENTAL METHODOLOGY Wednesday 12 February 2014 www.jamiesmind.co.uk 36
- 37. Learning Objectives By the end of this lesson you: • Must be able to do this … • Should be able to do that … • And maybe, if you’re good, do this … Wednesday 12 February 2014 www.jamiesmind.co.uk 37
- 38. Experiments • Independent Measures • Participants are only in one condition. Condition 1 Condition 2 Repeated Measures • The same participants repeat the two conditions Condition 1 Condition 2 Counter balancing – alter order of Pp’s Wednesday 12 February 2014 www.jamiesmind.co.uk 38
- 39. Experiment independent groups or repeated measures? Wednesday 12 February 2014 www.jamiesmind.co.uk 39
- 40. Independent Groups Remember these Banana Potato Sweetcorn Pear Tomato Pineapple Turnip Apricot Grape Carrot Apple Strawberry Wednesday 12 February 2014 www.jamiesmind.co.uk 40
- 41. Apricot Broccoli Onion Strawberry Tomato Pineapple Banana Sweetcorn Orange Carrot Turnip Lettuce Apple Lemon Raisin Potato Blackberry Wednesday 12 February 2014 Pear www.jamiesmind.co.uk Grape Cucumber 41
- 42. Repeated Measures Remember these Television Chair Curtain Video Wall Clock Table Sink Bin Desk Shelf Stool Wednesday 12 February 2014 www.jamiesmind.co.uk 42
- 43. Video Alarm Frame Television Box Wall Table Stool Chair Desk Shelf Curtain Sofa Heater Picture Clock Carpet Sink Wednesday 12 February 2014 Bin www.jamiesmind.co.uk Window 43
- 44. Strength Weakness Independent Measures No Order Effects Fewer Demand Characteristics Individual Differences Repeated Measures No Individual Differences Order Effects (counter balancing) Evaluation of Experimental Designs Wednesday 12 February 2014 www.jamiesmind.co.uk 44
- 45. Experiments Matched Pairs – make two groups of participants as similar as possible. Condition 1 Condition 2 Male 21 IQ = 105 Male 21 IQ = 105 Female 25 IQ = 115 Wednesday 12 February 2014 Female 25 IQ = 115 www.jamiesmind.co.uk 45
- 46. Strength Weakness Independent Measures No Order Effects Fewer Demand Characteristics Individual Differences Repeated Measures No Individual Differences Order Effects Matched Pairs Controls for Individual Differences (counter balancing) Can be difficult and costly. Evaluation of Experimental Designs Wednesday 12 February 2014 www.jamiesmind.co.uk 46
- 47. Validity Reliability Check Different methods to collect DV Replicate Improve Improve DV method Improve Controls Wednesday 12 February 2014 www.jamiesmind.co.uk 47
- 48. Wednesday 12 February 2014 www.jamiesmind.co.uk 48
- 49. Sampling Representative Sample Generalisations General Population Sampling Techniques Sample
- 50. Sampling Opportunity Sample Random Sample • People who are there at the time. • Each person in the GP has an equal chance of being chosen. • Quick / Cheap / Easy • Not representative • Expensive and time consuming. • Representative sample
- 51. Sampling Self-Selected Snowball Sampling • Participants volunteer to be in the sample following advert etc. • One person tells others who tell others … • Quick / Cheap / Easy • Not representative What kind of person volunteers for a psychology experiment? • Allows us to collect difficult to locate people. • Time consuming.
- 52. The population is the group of people from whom the sample is drawn. For example if the sample of participants is taken from sixth form colleges in a city, the findings of the study can only be applied to that group of people and not all sixth form students in the UK and certainly not all people in the world. Wednesday 12 February 2014 www.jamiesmind.co.uk 52
- 53. Obviously it is not (usually) possible to test everyone in the target population so therefore psychologists use sampling techniques to choose people who are representative (typical) of the population as a whole. = If your sample is representative then you can generalise the results of your study to the wider population. Wednesday 12 February 2014 www.jamiesmind.co.uk 53
- 54. Geek ! Want to be in my study? Opportunity sampling is the sampling technique most used by psychology students. It consists of taking the sample from people who are available at the time the study is carried out and fit the criteria you are looking for. Wednesday 12 February 2014 www.jamiesmind.co.uk 54
- 55. This is a sampling technique which is defined as a sample in which every member of the population has an equal chance of being chosen. Wednesday 12 February 2014 www.jamiesmind.co.uk 55
- 56. Volunteerslove I just needed for Sounds I’ve Gotta do psychological studyalways to be rubbish…hair.. wanted to be in my helpful…. on learning a study…. Self selected sampling (or volunteer sampling) consists of participants becoming part of a study because they volunteer when asked or in response to an advert. Wednesday 12 February 2014 www.jamiesmind.co.uk 56
- 57. = 60% female 40% male = 60% female 40% male Stratified sampling involves classifying the population into categories and then choosing a sample which consists of participants from each category in the same proportions as they are in the population. Wednesday 12 February 2014 www.jamiesmind.co.uk 57
- 58. 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 What is the when there is no distraction. distraction? How are we manipulating it? Operationalising your hypothesis How have you manipulated your IV? How have you measured your DV? Wednesday 12 February 2014 www.jamiesmind.co.uk 58
- 59. 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. Wednesday 12 February 2014 www.jamiesmind.co.uk 59
- 60. Alternate Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. Null Experiments – Hypotheses There will be no significant difference between participants who [do something] and those who [do something else]. Any difference will be down to chance. Wednesday 12 February 2014 www.jamiesmind.co.uk 60
- 61. Experiments – Hypotheses 1Tailed Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else]. 2Tailed There will be a significant difference between participants who [do something] and those who [do something else]. Wednesday 12 February 2014 www.jamiesmind.co.uk 61
- 62. Independent & Independent & Dependent Variables Dependent Variables Confounding & Confounding & Extraneous Variables Extraneous Variables Types of Types of Experiments Experiments Laboratory Laboratory Field Field Quasi (natural) Quasi (natural) Sampling Sampling Methods Methods Opportunity Opportunity Random Random Snowball Snowball Stratified Stratified Self-Selected Self-Selected Wednesday 12 February 2014 Experiment Experiment al Methods al Methods Cause & Cause & Effect Effect Independent Independent Measures Measures Repeated Measures Repeated Measures Matched-Pairs Matched-Pairs Ethics Ethics Ecological Validity Ecological Validity Reliability Reliability Validity Validity www.jamiesmind.co.uk ± 62
- 63. Key Terms - Experiments • • • • • • • • • • • Laboratory Experiment Field Experiment Quasi Experiment Independent Variable Dependent Variable Confounding Variable Extraneous Variable Replication Cause and Effect Ecological Validity Alternate Hypothesis Wednesday 12 February 2014 • • • • • • • • • Demand Characteristics Ethics Independent Measures Repeated Measures Matched-Pairs Individual Differences Order Effects Counter Balancing Operationalising Hypothesis • Null Hypothesis www.jamiesmind.co.uk 63
- 64. Data Analysis Nominal - measure of central tendency: mode Data in categories (finished, fell, started) Ordinal - measure of central tendency: median Data which are ranked or in order (1st 2nd 3rd) Interval - measure of central tendency: mean Precise and measured using units of equal intervals (1m54s, 1m59s, 2m03s) Measure of dispersion = range (Highest – Lowest) Wednesday 12 February 2014 www.jamiesmind.co.uk 64
- 65. Levels of Measurement • • • • Time Weight Length Number of ‘keepieups’ • Age (years old) Wednesday 12 February 2014 • Colours • Score on a test • Extroversion score on a scale of 1-10 • Money • Age (young / teenager / middle age / old) www.jamiesmind.co.uk 65
- 66. Descriptive Statistics measurement of central tendency (average) measurement of dispersion (range or standard deviation) graphs & visual displays Inferential Statistics statistical tests – making inferences from the results Wednesday 12 February 2014 www.jamiesmind.co.uk 66
- 67. Which Statistical Test? NOMINAL DATA ORDINAL DATA INTERVAL DATA REPEATED MEASURES Sign test Wilcoxon sign test Related t test* MATCHED PAIRS Sign test Wilcoxon sign test Related t test* INDEPENDENT MEASURES Chi-squared Mann-Whitney 'U' Unrelated t test* CORRELATION Chi-squared Spearman Rho Pearson moment* Wednesday 12 February 2014 www.jamiesmind.co.uk 67