experimental methods

EXPERIMENTAL METHODOLOGYHow science works

1Friday 7 April 2023 www.jamiesmind.co.uk

Can you test these? How? 1. You accidentally swallow about 8 spiders a year.2. You only use 10% of your brain.3. Men think about sex every seven seconds.4. There are more people than chickens in the world.5. The Great Wall of China is the only human-made

object visible from the moon.6. Sneezing seven times in a row is the same as an

orgasm.7. If you sneeze with your eyes open your eyes will pop

out of your head. 8. It is impossible to lick your elbow.9. Dogs and cats are colour-blind.10. Goldfish only have a 7 second memory.


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.

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!5Friday 7 April 2023 www.jamiesmind.co.uk


Research investigating if there is a difference between students who are deprived of sleep and students who have had plenty of sleep.


An experiment to investigate if men are more obedient than women when an experimenter asks them to inflict pain onto another person.


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.


We want to investigate if a person will remember images or words better having been exposed to them for thirty seconds.


Will white rats be able to run a maze quicker than grey rats?

Experiments

Independent Variable

(IV)

Dependent Variable

(DV)

cause effect


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 13Friday 7 April 2023 www.jamiesmind.co.uk

Experiments

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.

cause effect


• 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.


Review

Friday 7 April 2023 www.jamiesmind.co.uk 16

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

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?

Learning Objectives



• Must be able to list the ethical issues in psychological research.

• Should be able to describe the different types of controls in psychological research.

“[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, 200820Friday 7 April 2023 www.jamiesmind.co.uk

refers to an experimental

artefact where participants

form an interpretation of

the experiment's purpose

and unconsciously change

their behaviour accordingly

The experimenter effect is a term used to describe subtle cues or signals from an experimenter that affect the performance of participants in studies.

The experimenter effect is a term used to describe subtle cues or signals from an experimenter that affect the performance of participants in studies.

The cues may be unconscious nonverbal cues, such as muscular tension or gestures. They may be vocal cues, such as tone of voice.

The cues may be unconscious nonverbal cues, such as muscular tension or gestures. They may be vocal cues, such as tone of voice.

Ethics

Friday 7 April 2023 www.jamiesmind.co.uk 31

• Consent

• Deception

• Debriefing

• Withdrawal

• Confidentiality

• Protection

• Observation

• Advice

• Colleagues


Participants required to behead a live rat with a butchers knifeLandis (1924)

Children deliberately pressured psychologically to induce stuttering resulting in lifelong emotional suffering

Johnson et al. (1939)

Sheridan & King (1939)Participants required to administer electric shocks to puppies to such an extent that death occurred

Children fed extracts of stool from individuals infected with hepatitis

Willowbrook (1956)


The Ethics Love AffairHow 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.


Task

Some experimental Questions! You can use your personal notes or course reader.

Time: 20 minutes 35Friday 7 April 2023 www.jamiesmind.co.uk

Learning Objectives



• Must be able to do this … • Should be able to do that … • And maybe, if you’re good, do this …

Experiments

• 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


39

Experiment

independent groups or repeated

measures?

Friday 7 April 2023 www.jamiesmind.co.uk

Independent Groups Remember these

Banana Potato Sweetcorn Pear

Tomato Pineapple Turnip Apricot

Grape Carrot Apple Strawberry


Apricot Broccoli Pear Grape

Onion Strawberry Tomato Cucumber

Pineapple Banana Sweetcorn Orange

Carrot Turnip Lettuce Apple

Lemon Raisin Potato Blackberry


Television Chair Curtain Video

Wall Clock Table Sink

Bin Desk Shelf Stool


Repeated Measures Remember these

Video Alarm Bin Window

Frame Television Box Wall

Table Stool Chair Desk

Shelf Curtain Sofa Heater

Picture Clock Carpet Sink


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


Experiments

Matched Pairs – make two groups of participants as similar as possible.

Condition 1 Condition 2

Male21IQ = 105

Male21IQ = 105

Female25IQ = 115

Female25IQ = 115


Strength Weakness


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


Validity Reliability

CheckDifferent

methods to collect DV

Replicate

Improve Improve DV method

Improve Controls


Sampling

General Population

Sample

Representative Sample Generalisations

Sampling Techniques

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.

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.


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.


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.

Want to be in my study?

Geek!


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.


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.

Volunteers needed for psychological study on learning

Sounds rubbish…

Gotta do my hair..

I just love to be

helpful….

I’ve always wanted to be in

a study….


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.

= 60% female

40% male= 60% female

40% male


Experiments – Hypotheses

Participants memory will be much worse when there is a distraction in the room than when there is no distraction.


How are we measuring memory?

What’s better or worse? Higher /

Lower? More / Less?

What is the distraction? How are we manipulating it?

Operationalising your hypothesis

How have you manipulated your IV?How have you measured your DV?




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.



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.

Alte

rnat

eN

ull



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


Experimental MethodsExperimental Methods

±

Independent & Dependent Variables

Independent & Dependent Variables

Confounding & Extraneous Variables

Confounding & Extraneous Variables

Cause & Effect

Cause & Effect

Types of Experiments

LaboratoryField

Quasi (natural)

Types of Experiments

LaboratoryField

Quasi (natural)


Repeated Measures

Matched-Pairs


Repeated Measures

Matched-Pairs

Sampling Methods

OpportunityRandomSnowballStratified

Self-Selected

Sampling Methods

OpportunityRandomSnowballStratified

Self-Selected

EthicsEthics

Ecological ValidityReliabilityValidity

Ecological ValidityReliabilityValidity


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

• Demand Characteristics• Ethics• Independent Measures• Repeated Measures• Matched-Pairs• Individual Differences• Order Effects• Counter Balancing• Operationalising

Hypothesis• Null Hypothesis


Data AnalysisNominal - measure of central tendency: modeData 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: meanPrecise and measured using units of equal intervals

(1m54s, 1m59s, 2m03s)

Measure of dispersion = range (Highest – Lowest)


Levels of Measurement

• Time• Weight• Length• Number of ‘keepie-

ups’• Age (years old)

• Colours• Score on a test• Extroversion score on

a scale of 1-10• Money• Age (young /

teenager / middle age / old)


Descriptive Statisticsmeasurement of central tendency (average)measurement of dispersion (range or standard deviation)graphs & visual displays

Inferential Statistics statistical tests – making inferences from the results


Which Statistical Test?

NOMINALNOMINALDATADATA

ORDINALORDINALDATADATA

INTERVALINTERVALDATADATA

REPEATEDREPEATEDMEASURESMEASURES Sign testSign test Wilcoxon sign testWilcoxon sign test Related tRelated t

test*test*

MATCHEDMATCHEDPAIRSPAIRS Sign testSign test Wilcoxon sign testWilcoxon sign test Related tRelated t

test*test*

INDEPENDENTINDEPENDENTMEASURESMEASURES Chi-squaredChi-squared Mann-WhitneyMann-Whitney

'U''U'Unrelated tUnrelated t

test*test*

CORRELATIONCORRELATION Chi-squaredChi-squared SpearmanSpearmanRhoRho

PearsonPearsonmoment*moment*
