Conducting Experiments

Definition (#f7aeae)

Important (#edcae9)

Extra (#fffe9d)

Manipulating the IV:

  • Operational definition is needed for the variable being studied to be presented to the samples.

  • Method in which participants are selected would impact external validity

  • In manipulating the IV, the researcher then changes the conditions in which participants will be exposed.

  • Research also proceeds to “set the stage”:

    • Supplying participants with information necessary to provide an informed consent to participate.

    • Experimental setting must be plausible to the participants.

Types of Manipulation:

  1. Straightforward Manipulation:

    • IV is manipulated with simplicity by presenting written, verbal, or visual material to the participants.

    • For ex: Study on memory recall (phonological similarity). Words that are similar cat, map and words that were dissimilar mop, pen, and cow dissimilar words were recalled more accurately.

    • Most manipulations of an IV in all areas of research are usually straightforward, varying the difficulty of materials learnt, motivation levels, ways questions are asked.

  2. Staged Manipulation:

    • At times, it’s necessary to stage events during an experiment in order to manipulate the IV:

      • Research may be attempting to create some psychological state in the participant as in frustration, anger, lowering self-esteem.

      • To simulate some situation that happens in the real word.

    • Staged manipulations often employ the use of a confederate or accomplice.

  3. Complex Manipulation:

    • Strength of manipulation:

      • Simple experimental designs has 2 levels of the IV.

      • On the basis of what would result in the strongest manipulation that could maximise the difference to have the largest impact on the DV i.e. result in statistical significance.

    • Cost of manipulation:

      • Limited monetary resources limits ability to afford equipment or pay participants.

      • To run experimental conditions ‘individually’ on each participant may also require more time & cost, than running on multiple participants in a single shot.

      • Straightforward manipulations are then usually less costly.

Measuring the DV:

Types of Measures include:

  1. Self-report:

    • Would commonly use the aid of rating scales.

  2. Behavioural Measures:

    • Are direct observations of behaviours; quantified.

  3. Physiological:

    • Recording responses of the body. Ex: Galvanic Skin Response (GSR), or Electroencephalogram (EEG), measuring sleep stages, emotional arousal, or anxiety.

    • Researchers would go with a single DV, though most studies would also include more than 1 DV. Ex: Measuring wellness would include measuring eating habits, exercise frequency and stress/fatigue levels.

Controlling Experiments:

  1. Basic experimental design has 2 groups; experimental group receiving treatment and a control group that doesn’t.

  2. A control group allows to eliminate a variety of alternative explanations for the results, improving internal validity.

  3. Additional control procedures are necessary to address other types of alternative explanations.

  4. 2 general issues with control in an experiment: Participant vs Experimenter expectations.

Controlling for participants expectations:

  • Demand characteristics: Any feature of an experiment that might inform participants of the purpose of the study.

  • When participants form expectations about the hypothesis of the study, they will do whatever necessary to confirm or deny the hypothesis.

  • Solutions:

    • Use of deception to prevent participants from the true purpose.

    • Disguise the DV by using an unobtrusive measure, or by placing the measure among a set of unrelated filler items.

    • Assess the effects of demand characteristics by asking participants about their perceptions of the study.

  • Placebo groups: Used when unsure whether improvement is attributed to the properties of a drug or the expectation of the drug to work.

  • Solutions:

    • Placebo groups: participants receive a pill containing a harmless substance. If this group reacts as much as the experimental group, all improvement could be caused by a placebo effect.

    • Issue: Participants must be given treatment as soon as they have completed their part in the study to maximize the benefits of participation. Ethical consideration: Beneficence.

Controlling for experimenters expectations:

  • Experimenters are aware of the purpose of the study, and develop expectations on how participants should respond, and bias the results.

  • Experimenter bias or expectancy effects.

  • This could potentially happen when the experimenter is aware which condition the participants are in.

Keeping experimenters blind:

  • The person conducting the study or making observations is blind regarding what is being studied or which condition the participant is in.

    • Single-blind experiment: Participants are unaware which conditions are tested.

    • Double-blind experiment: Participants and experimenters are unaware which conditions are tested.

    • Done by hiring others to conduct the experiment & record observations for the researcher.

Additional Concerns:

  1. Research proposal:

    • Includes literature review to provide background of study; research questions to state intent of the study; procedures for details of how idea will be tested.

    • Put thoughts on paper help organise and structure ideas

  2. Manipulation check:

    • Initial attempt to directly measure whether IV has an intended effect on DV.

    • If the IV is ineffective, would save time from carrying out whole experiment.

  3. Pilot studies:

    • Researcher does a trial run on participants to provide opportunities to make necessary changes in procedures before running entire study.

  4. Debriefing:

    • Opportunity to interact with participants to discuss ethical and educational implications of study.

    • Provides opportunity to learn more about participants.