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  • Created by: Beth
  • Created on: 07-01-13 16:50

Empirical Evidence and Approach

Psychologists rely on scientific methods of acquiring knowledge to achieve their goals; this called empirical evidence. An empirical approach assumes that observations are not influenced by emotions or personal opinion; they are objective. It’s very difficult to do this is in psychology so psychologists have to be extremely careful about how they conduct their R.

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How science works

Observe human behaviour

Develop explanations and Hypothesis

Test Hypothesis

Collect Results

Draw Conclusions

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  • Validity: extent to which something measures what it is supposed to measure. Involves issues of control, realism and generalisability. But study can have high realism but lack generalisability.
  • Control: The extent to which any variable is held constant/regulated by a R it is important to control as many relevant EV’s as possible otherwise results would be meaningless as the R may have not actually tested what they intended to and instead the influence of another variable not the IV has been tested. 
  • Mundane Realism: Refers to how a study mirrors the real world. The simulated task environment is realistic to the degree to which experiences encountered in the environment will occur in the real world
  • Generalisability: Just because a study is conducted in a natural environment it does not mean you can generalise the findings to the real world e.g. if only use US uni students ‘though experiment may be in a natural setting’ can’t generalise results to all ages/cultures.
  • Internal validity (about control and realism) : extent to which study measures what it is set out to measure/degree to which the observed effect was due to the experimental manipulation rather than other factors such as EV'S which may affect results.
  • External validity (about generalisability): The degree to which the findings can be generalised to other settings (ecological validity), to other groups of people (population validity) or over time/to any era (historical validity). Can be affected by representativeness of the sample.
  • External Validity is affected by internal validity – you cannot generalise the results of the study if it was low in internal validity.
  • Sample validity:The extent to which the P’s represent people outside the R situation.
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Reliability: A measure of consistency both within a set of scores or items ( internal reliability) And also over time, such that it is possible to get the same results on subsequent ocassions when the meaure is used (external reliability).

Internal reliability: Whether a test is consistent within itself.

External reliability: Whether a test measures consistently over time.

The reliability of a experiment can be determined through replication.

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What is an experiment?

A scientific procedure undertaken to test a hypothesis.

Must have an IV and DV  to be an experiment

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Investigator and experimenter definition and bias

Investigator -  Design's the experiment/study

Experimenter -  Carries out the experiment/study

Investigator/experimenter/R bias: Effect of the investigator/experimenter expectations on a P’s behaviour and thus on the results. E.g. fast and slow learner rats in a maze

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Laboratory Experiment

 An experiment conducted in a special enviroment where variables can be carefully controlled.

+ Variables are easier to control in a lab comapred to a natural setting

+ High degree of control, since EV'S minimised = cause and effect can be determined if carefully controlled variables

+ If care taken in design and conduct, and has been reported accurately can be easily replicated (reliability)

- Artificial contrived situation where P’s may not behave as they do in everyday life because of a lack of mundane realism, P effects, investigator effects and demand characteristics – reduce internal validity

- Low ecological validity as it is difficult to generalise the results if the tasks given to the P’s are not like in real life (lacks mundane realism)

- Not everything can be investigated using a lab 

- Ethics (is an issue) - deception

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Experiments - Field Experiments

An experiment conducted in a more natural enviroment however the IV is still deliberately maniulated by a reseracher.

+ Can establish causal relationships by manipulating the IV and measuring its effect

+ Less artificial so higher mundane realism and thus higher internal validity.

+ Avoids P effects and  demand characteristics (because the P’s may not be they are in an experiment) which may increase internal validity.

- There still may be demand characteristics e.g. the way an IV is operationalised may convey the experimental hypothesis to P’s.

- Low internal validity as little control of extraneous variables and since conditions will never be the same again difficult to replicate.

- Ethics (is an issue) -  P’s may not have agreed to take part (not aware of participating) e.g. informed consent

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Experiments - Natural Experiments

A research  method where the experimenter can’t manipulate the IV directly but where it varies naturally and the effect can be observed on a dependent variable.

+ Enables psychologists to study real life problems  (increased mundane realism and validity).

+ Allows R where the IV can’t be manipulated for ethical or practical reasons.

+ High ecological validity – the setting is in a natural environment, so the data can usually be generalised.

+ R has little/no involvement with situation so P's unaware of being observed = few demand characteristics and reduced R bias. But P’s may be aware  = P effects, investigator effects and demand characteristics.

- Many extraneous/confounding variables (e.g. lack of random allocation to conditions and sample may have unique characteristics so) = low internal validity can't generalise R.

- Cannot demonstrate causal relationships because IV not directly manipulated.

- Can only be used where conditions vary naturally (and this happens rarely)

- Impossible to replicate in order to check validity and reliabilty / Ethics (an issue)-Protection if a sensitive subject

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Other Experiments

(but are not really experiments)

Difference studies: 2 groups of P’s are compared in terms of a DV (e.g. males vs. females) this is not a true experiment as the apparent IV hasn’t been manipulated. These are also quasi experiments

Quasi-experiments: Studies that are ‘almost’ experiments but lack 1 or more features of a true experiment, such as full experimenter control over the IV (so natural experiments are quasi experiments) and random allocation of P’s to conditions meaning that cannot claim to demonstrate causal relationships.

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