A2 psychology revision SECTION A EXPERIMENTS - G544 (approaches and research methods)

Experiments summarised.

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Psychology ­ Section A ­ EXPERIMENTS
Null ­ There will be no significant difference in the DV between the IV1 and IV2
Alternate ­ There will be a significant difference in the DV between IV1 and IV2
Alternate (one tailed) ­ There will be a significant increase/decrease in the DV for IV1 than IV2
Laboratory ­ a controlled experiment in a controlled artificial environment
Strength Weakness
Control = high reliability and less EVs Low ecological validity = not generalizable
Easily replicable and standardised = high reliability High chance of demand characteristics = low validity
Manipulation of the IV indicates cause and effect
Field ­ controlled experiment in natural environment related to the study
Strength Weakness
High ecological validity = generalizable and higher Less control = Higher chance of EVs affecting
validity reliability
High validity = in a natural environment (unaware) Harder to replicate = less reliable
Quasi ­ Naturally occurring variables in their occurring environment (lab or field)
Strength Weakness
High ecological validity = more valid Ethics (consent)
No manipulation of variables = ethical Harder to find participants due to there usually
being a smaller sample size = less generalizable and
less representative of the whole target population
Not classed as a true experiment
Independent measures ­ participants only participate in one condition alone
Strength Weakness
No order effects (fatigue, boredom and practice) = Need a larger number of participants = more time
more reliable consuming and harder to find
No demand characteristics = more valid Participant variables are harder to control for = low
Repeated measures ­ participants participate in both/all conditions
Strength Weakness
Less participants needed = less time consuming and Higher chance of order effects = less reliable
easier to find
Participant variables are controlled for Higher chance of demand characteristics = less valid

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Matched pairs ­ participants matched to another based on certain qualities that affect the study and then do an
independent measures design (each do the different conditions and are compared)
Strength Weakness
Control over participant variables Not all participant variables can be controlled for
Higher chance of demand characteristics More participants needed
Higher chance of order effects Deciding what to match on
Sampling methods:
Opportunity ­ Whoever is available at the time and happened to be there
Strength Weakness
Easy and quick Not representative of…read more

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Random sampling ­ Every member of the target population has an equal chance of being selected. (Out of a
hat or computer random number/name)
Strength Weakness
Unbiased Unethical
Inexpensive, quick and easy High chance of withdrawal
Extraneous variables
Participant variables ­ Characteristics of the participants that could affect the results.…read more

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Protection from harm
Analysing data
Means of central tendency:
-Mean: Add all together and divide by the number of variables
-Medium: Organize numbers in order and select the middle variable
-Mode: The most popular variable
-Range: The smallest to the largest numerical variable
Levels of data: (In order of least to most scientific)
-Nominal = Data is in separate categories, (including behavioural checklist). MODE.…read more

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Inferential Tests (No, I, C, M,R,S, Will, Smith)
Nominal Ordinal/Interval/Ratio
Independent Chi-Square Test Mann Whitney-U Test
Measures -Test for a difference -Test for a difference
-Nominal -Ordinal/Interval/Ratio
-Independent Groups Design -Independent Groups Design
Repeated measures Sign Test Wilcoxon Signed Ranks Test
Matched pairs -Test for a difference -Test for a difference
-Nominal -Ordinal/Interval/Ratio
-Repeated/Matched Pairs Design -Repeated/Matched Pairs Design
Spearmans Rho Rank Correlation Test
-Test for a relationship
-No design
Inferential statistical test of the experimental hypothesis finds the probability
Probability of 1…read more

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Split-Half Method tests whether a measure is high or low by splitting questionnaire in half and answering them
separately to give similar or the same results
External Reliability
The extent to which a test or procedure is consistent from one occasion to another on the same person
Eg, same results should be found on a test if repeated on different days in a different experiment or by
different researchers y one person
High: GSR, EMG, EEG, ECG, SIT sessions, Farrington and Juby questionnaire over years…read more

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Increase: Strong correlation
Face Validity
The measurement looks like it is measuring what it is supposed to
Affecters: Based on opinion, subjective and looking at the DV
Increase: Cannot because its due opinion
Affecters of validity
Demand characteristics = use deception, Independent measures or matched pairs and single blind technique
Participant variables = Variables are what affects the results rather than the measure and can't be compared so
use repeated and matched pairs
Sampling bias: Picking a sample to suit the study rather than represent…read more

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Psychology A2 ­ Approaches and research methods
Section A -
Experiments…read more

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