Week 2: Experimental design and method Flashcards

1
Q

What are the two types of research?

A

Quantitative- involves gathering numerical data
Qualitative- involves gathering non-numerical data

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2
Q

What are the principles of quantitative research?

A

-Involves gathering numerical data
-Always begin with a testable prediction (hypothesis)

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3
Q

What is the difference between a population and a sample?

A

Can’t gather data from whole population as too time consuming/costly + not all will respond
-Instead select a sample from population + gather data from them
-> instead we take a sample from the population and gather data from them
-We want to be able to generalise the results gained from our sample to the whole population we are interested in

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4
Q

What is random sampling and what are the 2 types?

A

Quite uncommon in psych
-Leads to a representative sample -> confident in generalising results to entire population

2 most common forms of random sampling:
- Simple random sampling: every single person in population has equal chance of being picked

  • Stratified sampling: population is divided into meaningful groups (e.g. where they live in the UK) + simple random sampling is conducted on each group
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5
Q

What is non random sampling and what are the three types?

A

Very common in psych
-Leads to a less representative sample -> less confident in generalising results to entire population
-Saves time + money + is often the only practical option when population is large (e.g. all people living in UK, or all males)

3 forms of non-random sampling:
- Voluntary sampling: members of the population self-select to participate in the research (e.g. those that reply to student advert). If ppts get their friends/family to participate this is an e.g of snowball sampling

  • Convenience sampling: members of the population who are easy to reach are asked to participate in the survey
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6
Q

How big should the sample be?

A

The size of the sample will determine:
- Extent to which you can generalise findings
- Probability of a ‘chance’ finding or of missing an important finding (larger sample = more power to detect an effect if it exists)

Depends on:
- Size + homogeneity of
population
- Nature of variables measured
- Required precision of results
- How confident you want to be about your results

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7
Q

What are experiments?

A

-The only way to explore causal relationships
-> Do changes in variable A cause changes in variable B?
Variable = any value that can vary (e.g. score on a test)
-Manipulate the values of one variable (A) and see if it affects a second variable (B), keeping all other variables constant
e.g. does exercise (A) affect memory performance (B)
- Want to control for chance differences between groups - can do this by random allocation to groups

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8
Q

How do we allocate the members of our sample to the groups?

A

We want to control for chance differences between groups
-> best way to do this is by random allocation to groups
-> each member of sample has equal chance of being allocated to either group

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9
Q

What are the variables in an experiment?

A

Independent variable (IV):
- The variable which you think may be a causal variable
- The variable that you manipulate (e.g. exercise level)
- Has two or more conditions/groups (e.g. regular exercise vs no exercise

Dependent variable (DV):
- The variable that you think is affected by the changes in the IV
- The variable that you measure (e.g. memory performance)

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10
Q

What are quasi-experimental studies?

A

A study where the researcher cannot randomly allocate ppts to the conditions of the IV
e.g. when the IV = biological sex
-> split into males and females

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11
Q

What is the difference between experimental and control groups/conditions?

A

Experimental condition (e.g. regular exercise)
- Condition where the IV (exercise) is present
- Can be several experimental groups e.g.:
group 1 - exercise once a day
group 2 - exercise once a week

Control condition (e.g. no exercise)
- Condition where the IV (exercise) is absent

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12
Q

What are extraneous variables?

A

Variables that can potentially affect the relationship between the IV + DV -> need to control for as many as possible
e.g. in exercise + memory example, a third variable (e.g age of ppts) may affect memory performance
-> Age would be the extraneous variable
- An extraneous variable is called a confounding variable if it differs systematically with the IV
e.g.all ppts in regular exercise condition are aged 20-22, while all ppts in no exercise condition are aged 80-82

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13
Q

How can you prevent extraneous/confounding variables?

A
  • Match the conditions on key variables
    -Balance age, sex, education etc
    -Can’t predict all possible extraneous variables
  • Standardised procedure
  • Randomisation of sample to the conditions
    -> Ensures equal dispersion of all extraneous variables
    Randomisation is the key element to true experiments
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14
Q

What are demand characteristics?

A

Where ppts guess the study’s hypothesis and (consciously or unconsciously) change their behaviour to support or not support the hypothesis
-> Hiding the study’s true purpose until the end can prevent this

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15
Q

What are experimenter effects?

A

The experimenter’s desire to support the hypothesis affects their behaviour (consciously or unconsciously)
-> If possible, the experimenter shouldn’t know which condition each ppt has been assigned to - this prevents experimenter effects

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16
Q

What are the 2 types of experimental design?

A

Between-groups design (or independent measures/between-ppts/between subjects)
Within-groups design (or repeated measures/between ppts/between subjects)

17
Q

What is a between-groups design?

A

Compare different ppts in different conditions

Advantages:
- No carry-over effects: Avoids one condition contaminating other condition
- Process is quicker for ppts (less likely to get bored or drop out)

Disadvantages:
- Individual differences have greater effect
- Need more ppts

18
Q

What is a within-groups design?

A

Compare same ppts in both conditions

Advantages:
- Effect of individual differences is reduced
- Fewer ppts needed

Disadvantages:
- Boredom, fatigue, drop-out
- One condition may contaminate the other:
-> Carry-over effects (e.g. practice)

19
Q

How can we solve carry-over effects?

A

Counterbalancing- Split ppts into two groups
- Half of ppts do condition A first, followed by condition B, then the other half of ppts do condition B first, followed by condition A
-Still a within-groups design as doing both conditions

20
Q

What is the null hypothesis?

A
  • Manipulation of the IV will have no effect on the DV
  • There will be no difference between the conditions
21
Q

What is the experimental/alternative hypothesis?

A
  • Manipulating the IV will cause a change in the DV
  • There will be a difference between the conditions
22
Q

Hypothesis testing: direction of effect

A
  • All experimental hypothesis must predict a difference
  • Hypothesis are either directional (one-tailed) or non-directional (two-tailed)
    -> determined by findings of prior research

e.g:
“there will be a difference in the speed of red and blue cars” -> two-tailed hypothesis
“red cars will travel faster than blue cars” -> one-tailed hypothesis

23
Q

Why do we need to operationalise our variables?

A
  • Not only being clear on what each variable is but also how to quantify the variable you are measuring (DV)
24
Q

What is the method and what are its 4 elements?

A
  • Gives a clear, succinct and detailed account of how you conducted the research
  • Allows a reader to replicate your research
  • Report what you did in past tense, and don’t justify why you did these things

4 elements:
Design: overall nature of the design in response to testing your hypothesis
Participants: people you included (and excluded) from study
Materials: what materials/equipment/instruments were used
Procedure: steps taken in putting the above together + running the study

25
Q

Describe the design section of method

A

For experiments:
- Type of design: within-groups or between groups
- What are the variables being measured? (IV + DV)
- What are the different conditions of the IV?

26
Q

Describe the participants section of method

A
  • Sampling strategy (how and from where)
  • Sample size
  • Important characteristics of sample -> age, sex, other characteristics relevant to study
  • Any inclusion or exclusion criteria (e.g. must speak English as first language)
27
Q

Describe the materials section of method

A
  • Only include specialised equipment - not pen, paper, ppt info sheet, consent form, debrief form
  • Only say what was used, not how
  • Any stimuli. that were used e.g. word lists, pictures, survey scales and where they were obtained - include a reference to the source
28
Q

Describe the procedure section of method

A
  • Describe precisely what was done from arrival of ppt to the debrief at the end
  • Should allow others to replicate your exact procedures
  • Be clear + precise and only include relevant info
  • For experiments, explain how ppts were assigned to conditions