Psychology - Experiments

What is reliability?

It is what measures whether it can be replicated and has the same results. (consistency)

Validity

The extent to which something is true

two types of Validity

Internal Validity- to the extent to which the findings are due to the mechanisms/variables suggested and not confounding variables , is it set out to measure what its meant to

External Validity- to the extent of the results can be generalised

External vakidity types

Population Validity- can the research be generalised to other people outside the study… relates to sample, sample size, sampling method
Ecological Validity- research can be generalised to other settings … relates to type of research method, if study setting is realisitc

now do some practice on identifying experiment types and validity! internet ;)

another name for internal validity

Experimental Vaidity as it relates to whether or not the experimental design did the job it was set to do

What threatens Internal Validity?

Demand Characteristics - refering to clues that researchers leave that cause pts to behave in a certain way to match these expectations, potentially biasing the results

Field Experiment

an experiment in a natural setting of the pts, the IV is intentionally manipulated to produce change in DV

When is field experiments used

Used when it is important to take account of the natural environment

Pros of Field Experiment

• imrpoved ecological validity (avoiding fake setting means were more likely to generalise findings to real life situations)

• reduction of demand characteristics (natural enviroment=pts dont know theyre in study)

Cons of Field Experiment

• establishing control over extraneous variables is harder (bc its less controlled)

• can’t generalize findings (take place within particular environmental, cultural, social, or institutional settings that are unique and not easily replicable elsewhere)

Natural experiment

IV in a natural experiment involves a naturally occuring event, IV is NATURAL the setting is not, no direct control over IV

Why is the natural experiment not a true experiment?

Bc pts have not been randomly assigned

Quasi Experiment

almost like a experiment - under controlled conditions, variables/IV just simply exsist and are not manipulated

Both wuasi and natural …

use a pre exsiting IV which cannot be manipulated

Pros of quasi/natural

• decrease of demand characteristics (applies best to natural)

• allows us to study effects on behavior of IV that would normally be unethical for experimenter to manipulate

Cons of Quasi/ Natural

• loss of control therefore reducing idea of cause/effect occuring (since IV isnt under direct control)

• Pts not randomly assigned to conditions and therefore is a confunding variable

in a quasi there could be what

more differences other than IV that can account for results

Lab Experiment