measurements and variables Flashcards
the “how” of quantitative research
- the conclusions that we can draw from research depends on how the knowledge was generated
- for any piece of research we plan, we must be able to answer:
1) how do we actually test hypotheses appropriately?
2) how do we generalise our findings?
3) how do we quantify seemingly unquantifiable things? - the answer to these questions lies in research design
- research designs can vary on lots of different dimensions:
1) some designs involve multiple measurements from the same people and some design compare groups.
2) Some designs take all their measurement at one point and others follow participants across time. - the design we choose depends on:
1) our hypothesis
2) the resources we have (time, money, facilities)
3) logistical considerations
4) ethical considerations
structure
- start with a research question - hope it will answer our research
- come up with a hypothesis - we specify the outcome we expect
- to test the hypothesis we’ll design an experiment
testing our hypothesis
experiment might be like:
1) Invite a group into the lab.
2) Give half the people some ice cream to eat, and don’t give any ice cream to the other half (our manipulation).
3) We then get all participants to look at pictures of people (the stimuli) and rate how much they want to eliminate them on a scale from 0 (no desire) to 9 (all the desire possible).
- after the experiment we might thank the pps and debrief them by describing the aims of the study
- in our study we’re manipulating one thing and measuring on thing
- our study has an independent and dependent variable
dependent variable
- you analyse it
- its value depends on the value of other variables
- its the things we measure and is sometimes called the outcome
independent variable
- influences the values of your dependent variable
- is the thing we’re manipulating and is sometimes called the predictor
features of a good study
- in a well-designed experiment, we can be confident in saying our manipulation caused a change in our outcome
- but this isn’t the case with our study, because we’re missing a lot of things.
- including:
1) controls
2) randomisation
3) blinding
4) a theoretical framework
controls
- Our imaginary study didn’t use any controls.
- We recruited all kinds of people without giving consideration to how different characteristics might affect our results.
1) Children and adults in our sample
2) People with lactose intolerance in our sample who would’ve experienced discomfort eating ice-cream. - We didn’t have standardised instructions for participants who enrolled in the study.
3) Maybe some participants arrived very hungry, and others arrived very full, and the hungry participants were just hangry. - We didn’t control our IV appropriately - we might have often changed the brand, the flavour, or the amount of ice cream, maybe one day we gave frozen yoghurt instead of ice cream.
4) Now we don’t know exactly what caused any changes in the outcome.
5) It could be that inky strawberry mini milks cause murderous tendencies. - We didn’t control the lab environment it was conducted in, on some days the heating was up super high and on others we had the windows wide open.
- Maybe people only felt murderous when they were made to eat ice cream in the cold.
randomisation
- Another feature that might have been missing from our study is randomisation.
- We didn’t randomly assign people to the groups.
1) Maybe we recruited all our participants for the ice cream conditions first, and we did this outside of a dentists office.
2) It might be that most of these participants had sensitive teeth and so eating cold food made them angry. - A well-designed experiment should randomise both participant allocation and stimulus presentation order.
blinding
- Another feature that might have been missing from our study is blinding.
- Maybe we told participants that we were interested in the effects of ice cream on murderous tendencies
1) Participants may have modified their behaviour to fit or contradict our hypothesis. - Maybe we also gave all the participants the ice cream ourselves.
2) If participant are naive to group allocation then the study is said to be single-blind. - If neither the participants nor the researcher know which condition the participants are put in, the study design is known as double-blind.
Allocation is recorded but only revealed once the study is over and the data are being analysed.
theoretical framework
- the choice of predictor (IV) and outcome (DV) variables does not happen in a theoretical vacuum
- these choices should be base on theory, but in our experiment these choices weren’t based on theory
- it could be that murder causes people to eat ice cream, in which case we should probably swap the IV and DV
- or it might be that they’re completely unrelated and any effect is just a coincidence
types of experimental studies
- true experiments
- quasi-experiments
- natural experiments
true experiments
- usually have tight controls
- can be somewhat artificial, because they abstract away from the real world
- lack ecological validity - ability to generalise the results from an experiment to the real world.
- provide the most rigorous methodology for investigating casual relationships
- experiments can be difficult to perform from a logistical point of view, because randomisation can be difficult, and sometimes manipulating IVs directly can be difficult or impossible
quasi-experiments
- similar to true experiments except for participant randomisation
- this makes them useful in situations were randomisation isnt possible
- in situation like this, we should still try to match the pps so that the groups dont differ on any relevant characteristics, except for the ones we’re investigating
natural experiments
- studies where randomisation and manipulation occur through natural or socio-political processes
- one example might be twin studies:
1) Identical twins share essentially 100% of their genes.
2) Fraternal twins share on average 50% of their genes.
3) Both kinds of twins tend to share the same home environment (raised together).
4) Comparing similarities between identical twins and similarities between fraternal twins, we can estimate the role of genes and environment in all sorts of things (physical, mental health, personality, cognitive ability, etc). - Other kinds of natural experiments might be a result of policy changes (like smoking bans, or changes in the length of compulsory education) or natural events.
within-subject and between-subjects design
- in between-subjects or independent designs we compare different groups of pps - different pps are assigned to different conditions
- in within-subjects or repeated measure we take repeated measurements from pps - where each pps gets assigned to all the conditions and we compare
- mixed designs have both within-subject and between-subject manipulations - we split people into 2 groups but still measure each person under multiple conditions
- within-subject have some disadvantages like order effects, but with within-subject it can sometimes be easier to detect differences between conditions