the experimental method

• what is the IV?

  the IV is the factor that causes a change in the other, manipulated by the experimenter
• what is the DV?


  the factor that is changed by the IV, measured by the experimenter
• what is operationalisation?


  putting units of measurement on the variables. eg, amount of sleep (hours), intelligence (IQ).
• what is a hypothesis?

  a predictive statement
• what is a null hypothesis?

  a predictive statement that predicts there will be no difference in the results of the manipulated IVs.

  
  

  make sure to operationalise when writing hypotheses
• what is the writing frame for a null hypothesis?

  There will be no significant difference (in the DV) between (first IV) and (second IV). any difference found will be due to chance alone.
• what is an experimental hypothesis?

  a directional or non-directional hypothesis
• what is a directional hypothesis?

  one tailed. certain of the outcome.
• give an example of a directional hypothesis.


  participants who slept for longer (hours) will score higher in their maths test than participants who slept for less time.
• what is a non-directional hypothesis

  two-tailed. unsure of outcome
• give an example of a non-directional hypothesis.


  there will be a significant difference in the test scores of those who slept more and those who didn't sleep.
• name the three types of experiments.

  laboratory, field, quasi (natural).
• what is a laboratory experiment?

  a laboratory experiment is conducted in a lab and eliminates as many extraneous variables as possible. IV manipulated by the experimenter
• give two advantages of laboratory experiments.

  1- the highly controlled environment eliminates all extraneous variables, causing the study to have a high internal validity as the experimenter can easily establish cause and effect, therefore can be sure that the study is measuring what it claims to.

  2- easily replicable, so has a high external reliability
• give two disadvantages of laboratory experiments.

  1- not a lot of space so a small sample must be used. reduces external reliability- study could be a fluke

  2- causes the study to lack mundane realism therefore ecological validity as the highly controlled environment does not reflect everyday settings, so the hawthorne effect may cause participants to act differently than they usually would, and results cannot be generalised to natural settings.
• what is a field experiment?

  carried out in a natural environment. IV manipulated by the experimenter
• give two advantages of field experiments

  1- allows for a larger sample size

  2- has mundane realism therefore a high ecological validity as the natural setting reflects everyday environments, so the hawthorne effect will not cause participants to act differently than they usually would, and results can be generalised to natural settings.
• give two disadvantages of field experiments

  1- the environment isn't as controlled so there could be extraneous variables, reducing the internal validity, so it is difficult to establish cause and effect and the experimenter cannot be sure that the study is measuring what it claims to measure.

  2- not easily replicable
• what is a quasi experiment?


  an experiment in which the IV naturally occurring so is not manipulated, as the difference ready exists. eg, male and female
• give one advantage of quasi experiments.

  1- good for conducting ethical research- sometimes is the only ethical experimental method, as it. an be unethical to create a change in a naturally occurring IV.
• give two weaknesses of quasi experiments

  1- the IV is naturally occurring, therefore cannot be manipulated, so it can be difficult to establish cause and effect therefore internal validity is lowered

  2- can be difficult to replicate as the sample is often scarce.
• what is experimental design?


  The different ways in which the testing of participants can be organised
• what are demand characteristics?

  features of an experiment that indicate to the participants the aims of the experiment so that they act differently, causing the hawthorne effect
• what is independent measures design?

  different participants are grouped into different conditions, and participants take part in the study in only one condition.
• what are 2 advantages of independent measures design?

  different participants are grouped into each condition, therefore participants only undertake the study in one of the conditions,so they are less likely to detect demand characteristics, increasing the internal validity.

  participants are grouped into each condition, so each participant undertakes the study in only one condition which eliminates the order effect- this is because participants are less likely to become bored or unmotivated due to repetition, which ensures that the results are valid.
• what is a disadvantage of independant measures design?

  different participants are grouped into every condition, meaning that participant variables could affect results and make them unrepresentative, as some groups may be higher or lower in levels of a certain characteristic than others.
• what is a single blind trial?

  an experiment where the participant doesn't know the condition that they have been assigned to
• what is a double blind trial?

  an experiment where neither the individual nor experimenter know which group the participant is assigned to in order to prevent the experimenter from subconscious treating them in a biased way
• what is repeated measures design?


  each participant is tested on for every condition.
• what is an advantage of repeated measures design?


  individual differences between participants will not influence the results, as participants undertake the study in every condition, so they aren't grouped into conditions
• what are the disadvantages of repeated measures design?


  each participant is used for every condition so the participants are tested on a multitude of times so are more likely to notice demand characteristics, causing the hawthorne effect- they act differently than they usually would.

  
  

  each participant is used for every condition so the participants are tested on a multitude of times so are likely to become bored or unmotivated, meaning the order effect can affect the validity of results.
• what is the matched participants design?

  different participants are grouped into each condition, however, each group contains participants with a range of levels of a certain characteristic.
• what are the advantages of matched participants design?

  particioants are grouped into conditions with other particioants with a range of levels of a certain characteristic, so participant variables cannot affect results.

  
  

  participants are only tested on for one condition, meaning that the order effect is not likely to make participants become bored or unmotivated, so results are valid.

  
  

  participants are only tested on for one condition, meaning that they are less likely to notice demand characteristics so the hawthorne effect is eliminated, so participants act as they usually would
• what is a weakness?

  matching partners is time consuming
• what is opportunity sampling?

  Taking the sample from people who are available at the time
• what is a pro of opportunity sampling?

  quick and time efficient
• what is a con of opportunity sampling?

  not necessarily representative as researcher bias could have caused the researcher to choose participants based on similar characteristics.
• what is self selecting?


  participants volunteer themselves to take part through advertising such as posters and flyers.
• what is a pro of self selecting?


  less chance of sample attrition as participants volunteered willingly.
• what is a con of self selecting?

  motivation may act as an extraneous variable, as participants clearly are willing to take part therefore may put more effort into the study, causing them to act differently than they usually would which lowers the internal validity as the study possibly isn't measuring what it claims to measure.

  
  

  there is a chance that not many people see the advertisements, leading to a small sample and low external reliability.