Experimental methods.

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Key concepts.

Aim

  • A general statement of what the researcher desires to investigate.

Hypothesis

  • A statement in which the researcher believes is true.
  • A hypothesis should be operationalised.
  • Operationilased is something that can be measured and is clearly defined.
  • Directional hypothesis- is a specific statement about what the overall conclusion of the experiment/observation will be.
  • Non-directional hypothesis- a statement which doesnt express speficially how something will change but just that there will be a difference or correlation etc.

Experimental method

  • A researcher changes the IV and records the effect of the IV on the DV
  • DV is measured.
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Research issues.

Extraneous and confounding vairables

  • Extraneous vairables- these are vairables that are in the experiment/observation however, are undesired. the 'nuisance' vairable.
  • Confounding vairables- these type of vairables are vairables that the researcher fails to eliminate or control, they affect the DV making it more difficult for the researcher to understand if the IV affected the DV or the CV. CV's must be controlled.

Demand characteristics

  • Demand characteristics is the term used when a participant figures out or understands the true aim of the study due to observing the researcher or the actual experiments that giving the aim and changes their behaviour in order to match the criteria of the experiment.
  • Demand characteristics are undesired and badly affect the internal validity of the experiment.

Investigator effects

  • Any effect of the investigator's behaviour on the out come of the research (The DV).
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Research techniques.

Research techniques refer to a set of proceduresd used to collect data as a part of psychological research.

  • Randomisation- Refers to the use of chance wherever possible to reduce the researchers effect and hopefully demand characteristics.
  • Standardisation- This is where all participants in the trial are exposed to the exact same condition to reduce extraneuos vairables.
  • Control groups- Are used for the purpose of setting a comparison.
  • Single blind- The participant doesnt understand the true aim of the experiment, this in hope of stopping demand characteristics, however, this can lead to ethical issues being raised.
  • Double blind- The participant and the researcher both do not know what the aim of the investigation is and attempts to reduce researcher bias.
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Independent Groups

  • Independant groups are where one group of participants acomplish one condition of the experiment and another group of participants complete a different condition.

Advantages

  • No Order effects - Participants are exposed to the experiment once, this means that the participants should not become bored or tired therefore reducing the chance of Confounding vairables.
  • Natural behaviour - Participants are only going to do the experiment once, this means they are less likely to attempt to work out the true aim of the study which would affect the internal validity of the study, therefore reducing demand characteristics.

Disadvantages

  • Participant vairables - The participants of each groups are not the same, this will make it difficult for the researcher to investigate whether it was IV or PV affecting the DV.
  • More participants - More participants are required this means the investigation will be even more expensive.
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Repeated Measures

  • The same participants take part in all conditions of the investigation.

Advantages

  • Participant vairables - The participants are exposed to the exact same scenario therefore reducing confounding vairables as the group are the same.
  • Fewer participants - Because there is only one group of particpants are needed this means that the investigation is low cost.

Disadvantages

  • Order effects - Particpants may do better or worse when doing the same or similar task twice, this will reduce the validity of the findings.
  • Guessing aims - Because the participants are doing the same test twice they may feel more inclined to attempt and discover the aim, if they do figure it out they will most likely change their behaviour to fit the expectations of the research.
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Matched Pairs.

  • Two groups of participants are used however, the participants of eached group are paired together based on a common intrest they share for example bad eye sight.

Advantages

  • Particpant vairables - Participants are matched together based on a common intrest that is related to the experiment/investigation, this massively improves the validity of the experiment.
  • No order effects - Participants are only tested once, this enhances the validity of the results.

Disadvantages

  • Ineffective - Matching is very time consuming and sometimes does not work well either with the participants or with the actual investigation. Internal validity is thereby affected by the results.
  • More participants - Twice as many participants are required as opposed to match pairs.
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