Experimental method Flashcards
What’s an experiment?
research method where a causal relationship can be drawn because the IV is deliberately manipulated to observe the causal effect on the DV.
What’s an aim
A general statement about what the researcher intends to study —> states the purpose if a study
What’s a hypothesis
a precise statement which clearly states the relationship between the variables that are being investigated.
What are the 4 types of hypothesis?
Directional (one tailed)
Non-directional (two tailed)
Experiment/ alternate
Null
What’s a directional hypothesis?
predicts the nature of the effect of the independent variable on the dependent variable .
e.g. adults will recall more words than children
What’s a non-directional hypothesis?
states an expected diffrence but not the direction of results e.g. there will be a difference between the number of words recalled by adults than by children.
What’s an experimental/ alternate hypothesis?
A hypothesis in the context of an experiment —> predicts a difference or an effect between two variables.
What’s a null hypothesis?
predicts there won’t be a difference or effect between two variables
e.g. there won’t be a difference between the number of words recalled by adults compared to children.
What is an experimental design?
the different ways in which the testing of ppts can be organised in relation to the experimental conditions.
What are the 3 experimental designs?
Independent groups
Matched pairs
Repeated measures
What is independent groups?
Participants are randomly allocated into two conditions. One group does the experiment with variable 1, the other group does the experiment with variable 2. Results are compared.
What’s repeated measures?
Participants are not divided into groups. Instead, all participants do the experiment with variable 1, then afterwards the same participants do the experiment with variable 2. Results are compared.
What’s matched pairs?
all ppts take part in both conditions
+/- IDG
-More ppts needed
-Least effective design for controlling extraneous or confounding variables.
+Reduces the chance of demand characteristics
+Random allocation
+/- MP
-More ppts needed
-Not possible to match all ppt characteristics
+Use identical twins
+Good attempt to control ppt variables
+/- RM
-Demand characteristics
-Ppts may guess the purpose of the experiment
+Fewer ppts needed
+Can reduce order effects through counterbalancing
What’s counterbalancing?
A technique used to counteract order effects: ABBA half ppts do condition A then B and the other half do B then A.
What’s the IV?
The variable that’s manipulated
What’s the DV?
Measured
What’s operationalisation?
How IV is manipulated and how DV is measured
What’s an extraneous variable?
Additional variable to the IV that should be account for and controlled to avoid the impact on the DV.
E.g. time of day
What’s a confounding variable?
A variable that may have impacted the study that hasn’t been controlled and may affect the nature of the study e.g. IQ
What are demand characteristics?
Any cue that makes the ppt unconsciously aware of the aims of a study that helps ppts work out what the researcher expects to find.
What are investigator effects?
Anything that an investigator does that has an effect on the ppts performance in a study other than what was intended.
What’s randomisation?
Use of chance to reduce the effects of bias from investigator effects.
What’s standardisation/ standardised procedures?
A set of procedure that are the same for all ppts in order for the study to be replicable
How many types of experiment are there?
Lab
Field
Natural
Quasi
What’s a lab study?
An experiment in an artificial environment where variables can be strictly controlled.
+/- lab
+high degree of control
+replicable
-experimenter bias
-low ecological validity
What’s a field experiment?
An experiment conducted in a natural environment but IV is still controlled.
+/- field
+naturalistic
+controlled IV
-ethical considerations (informed consent)
-loss of control
What’s a Quasi experiment?
Experiment where the IV hasn’t been determined rather than instead of it naturally occurring e.g. gender difference studies
+/- quasi
+controlled conditions
-can’t randomly allocate ppts
What’s a natural experiment?
An experiment in an in the IV isn’t brought about by the researcher and would’ve happened even if the researcher hadn’t been there.
e.g. if studying reactions for to earthquakes
+/- natural
+provides opportunities
+high external validity
-natural occurring events
-very difficult to randomise
What’s sampling?
The group of ppts the researcher is interested in / testing
What are the 5 types of sampling?
Opportunity
Random
Systematic
Stratified
Volunteer
What’s opportunity sampling?
Ppts happen to be available at the time of the study - recruited conveniently
+/- opportunity
+time saving
+cost efficient
-not representative
-researcher bias
What’s random sampling?
When all members of the sample have an equal chance of being selected
Uses methods:
Lottery
Random number generator
+/- random
+no researcher bias
-time consuming
-volunteer bias: ppts can refuse to take so can end up with an unrepresentative sample
What’s systematic sampling?
Every nth member is selected from the sample
+/- systematic
+usually fairly representative
-not truly unbiased
What’s a stratified sample?
Composition of the sample reflects the varying proportions of people in a particular strata within the wider population
+/- Stratified
+no researcher bias
+representative data due to proportional strata
-time consuming
-identified strata can’t reflect all differences between people of the wider population
What’s a volunteer sample?
Self selection - ppts offers to take part either in response to an advert or when asked to
+/- volunteer
+easy and not time consuming
+more likely to corporate in the study
-volunteer bias
What’s a pilot study?
Small-scale version of an investigation which is done before the real investigation is undertaken
What’s a single-blind procedure?
A research method in which the researcher doesn’t tell the ppts if they’re given the treatment or placebo
Avoids demand characteristics
What’s a double-blind procedure?
Neither the experimenter or researcher knows who is receiving the treatment
