experimental method

experiment

a research method where causal conclusions can be drawn because an IV has been deliberately manipulated to observe the causal effect on the DV

4 types of experiment: lab, field, natural, quasi

experimental aims

- a clear and precise statement of the purpose of the study. states why a research study is taking place.
- should include what is being studied and what the study is trying to achieve
- it’s important that aims created in research are realistic and ethical

hypothesis

- a precise and testable statement that predicts what the researcher expects to happen in their research
- operationalisation is a key part of making the statement testable
- the research study itself is thus a means of testing whether or not the hypothesis is supported by the findings
- if findings support hypothesis then hypothesis accepted, if not, hypothesis rejected
- 2 main types of hypotheses: null and experimental
- stated at the beginning of the research and after carrying out statistical analysis on the results the experimenter either accepts or rejects the null hypothesis

null hypothesis

- states that the IV will have no significant effect on the DV
- there will be no difference between the two conditions, any difference is due to chance

what are the two types of experimental hypotheses?

1. non-directional hypothesis (two-tailed): states that the IV will have an effect on the DV but does not predict how it will affect the result. no previous research, or findings from earlier studies are contradictory.

2. directional hypothesis (one-tailed): states that the IV will have an effect on the DV and what that effect will be (the direction of the results). only used if there’s previous research studies that suggest a particular outcome.

what are the two main variables when it comes to psychological research?

1. independent variable

2. dependent variable (DV): the variable that is measured by the researcher. any effect on the DV should be caused by the manipulation of the IV.

cause-and-effect relationship

the IV has been the only variable to effect the DV

high internal validity

researcher confident they’ve measured what they intended to measure (i.e. the effects of just IV on DV) and all EVs have been controlled and there are no CVs in their study

extraneous variables (EVs)

not wanted cuz they can affect the DV and reduce the validity of the findings of the study

controlling EVs:
- researcher’s main concern is looking at the effects of just IV on DV, in order to do this all EVs need to be controlled
- between control and experimental conditions the only thing that should change is the IV, all other variables should remain consistent
- if all EVs are controlled, the research has been carried out successfully and the researcher can establish a cause-and-effect relationship → experiment has high internal validity

by conducting a pilot study before they carry out their main experiment researchers can ensure there are no EVs in their experiment.

pp variables, demand characteristics, situational variables, experimenter effects, investigator effects

participant variables

refers to anything specific to the pp that could affect the DV, e.g. age, gender, intelligence, etc.

demand characteristics

- environmental clues in an investigation that cause pps to work out the aim of the experiment and so they behave unnaturally
- pps respond in one of three ways: 1. attempt to please the experimenter (please U effect), 2. attempt to ruin the results (‘screw you’ effect), 3. become more self-conscious
- reduce the validity of the findings

situational variables

the experimental setting and surrounding environment must be controlled between conditions to avoid them impacting on the results, e.g. temp, time, etc.

investigator effects

- any effects of the investigator’s behaviour (conscious or unconscious) on the DV
- may include anything from the design of the study to the selection of, and interaction with, pps
- can include expectancy effects and unconscious cues or actions of the researcher (e.g. leading Qs, non-verbal communication) that are related to the study’s design e.g. the selection of pps, the materials, the instructors, etc. (active effect - due to their actions)

operationalising IVs and DVs

- fully defined and made measurable.
- enables another psychologist to replicate the research and is essential in establishing reliability.
- clearly describing the variables (IV and DV) in terms of how they will be manipulated (IV) or measured (DV)

ways of controlling extraneous variables

if an EV isn't controlled and interferes with a study this would prevent the researcher from establishing a cause-and-effect relationship → low internal validity → researcher won’t be able to conclude that the IV is the only variable to effect the DV as an EV has been present in the study

when a study is carried out with an EV present, this EV becomes a CV due to the fact that it's presence confounds the results of the study

randomisation, standardisation, counterbalancing, placebos, single-blind procedure, double-blind procedure

randomisation

- the use of chance to reduce the researchers influence on the design - controls investigator effects.
- e.g. in a memory experiment if pps are recalling words from a list the order of the list should be randomly generated so that the position of the each word is not decided by the experimenter.

standardisation

- all pps should be subject to the same environment, info and experience
- it’s important to make sure that each pp did exactly the same thing in each condition, otherwise the results (DV) might vary cuz of changes in the procedure rather than cuz of the IV
- all procedures should be standardised which includes the use of standardised instructions (a list of instructions for all pps that is the same for all people) which are read to each pp.

counterbalancing

controls for order effects in a repeated measures design - half the pps experience the conditions in one order and the other half in the opposite order.

placebos

- a treatment that has no effect on the behaviour being studied, it contains no active ingredient
- thus, it can be used to separate out the effects of the IV from any effects caused merely by receiving any treatment

single-blind procedure

controls for demand characteristics as the pp isn’t aware of research aims and/or of which condition of the experiment they’re receiving

double-blind procedure

neither the pp nor the researcher conducting the study are aware of the research aims or other important details of a study and thus have no expectations that might alter a pp’s behaviour so it controls for demand characteristics and investigator effect.

generalisation

the ability to apply the research findings to the entire target population - beyond the particular research setting and to help us understand behaviour in everyday life.

reliability

- the extent to which results similar each time, they’re carried out using the same procedures and design.
- if findings from research are replicated consistently, they are reliable.

experimental method

- a controlled situation in which the researcher manipulates one variable (IV) to discover its effects on another variable (DV), while the other variables are held constant.
- this allows the researcher to establish cause-and-effect.

validity

- how true and accurate the findings are - whether the research or test measured what it intended to measure
- it is important that research or a test is valid in order for the results to be accurately applied and interpreted
- 2 main types of validity: internal validity and external validity

external validity:
- the extent which the results of a study can be generalised to other real life setting (ecological validity) other people (population validity) and over time (temporal validity).
- many things can affect the realism of a psychological study. ‘mundane realism' - how a study mirrors the real world. the research environment is realistic to the degree to which experiences encountered in the research environment will occur in the real world.
- If the setting / materials used is too artificial or false, then the pps won’t act as they would normally.
- population validity: the extent to which the results of a study can be generalised to other people
- temporal validity: the extent to which the results of a study can be generalised over time

variables

a variable is something that changes in an experiment - it varies

IV: an aspect of the experimental situation that is manipulated by the researcher - or changes naturally - to see its effect on the DV

DV

EV: any variable other than the IV that may have an effect on the DV if it’s not controlled

confounding variable: any EV that isn’t controlled and thus affects the DV. variables vary systematically with the IV.

why do researchers need to control EVs?

so they can be sure IV affected DV → otherwise can’t draw conclusion about cause-and-effect

experimenter effects

- when the experimenter influences the pps or interprets the data to arrive at the results they’re seeking to obtain
- typically done subconsciously, though it may be done consciously as well
- anything specific to the experimenter that could affect the results of the research, e.g. gender, race, age, etc.

mundane realism

- refers to how a study mirrors the real world
- the research environment needs to be realistic of the real world

ecological validity

the extent to which the results of a study can be generalised to real life settings

experimental/alternative hypothesis

predicts there will be a difference between the two conditions

situational variables

variables that are connected with the research situation

participant variables

variables that are connected with the research pp (individual differences)