types of experiment

• Laboratory experiments

  -          Direct manipulation of an iv which is operationalised so is the dv

  -          High levels of control and aims to control extraneous variables /confounding variables so only difference between conditions is the iv.

  -          Also, a control group to act as a control with no manipulation but the dv is still measured which allows a baseline measurement for comparison –
• Laboratory experiments

  -          High levels of control allow for cause and effect to be established between the iv and the dv.

  -          Randomization – participants are randomly allocated to conditions – toss a coin to reduce extraneous variables associated with participants from affecting dv.

  -          Other factors of randomisation include the order stimuli s presented to participants and the order the participants take part in – to reduce order effects.

  -          Counterbalancing also used randomisation.
• Laboratory experiments

  + strength of lab experiment = can be easily replicated – because of high levels of control and allows for reliability to be checked and see if results are consistent

  + strength of lab experiment = high internal validity – because its easy to control potential confounding variables in a lab than in other settings so we can be sure the only factor affecting the dv is the iv – and increased ability to establish cause and effect between variables being measured
• Laboratory experiments

  Weakness of lab experiment = high control reduces ecological validity – experiment is likely to become artificial and therefore dosnt reflect real life situations – which then causes question on the accuracy of results and their ability to measure the complexity of human behaviour – emotions and motivation behind our actions
• Laboratory experiments

  Weakness of lab experiment =issue of demand characteristics – participants know they are being researched and may feel more inclined to act in a way they think is required – they have actively given up there time to participate in the study – this is an issue if participants are showing demand characteristics the measurement of the dv is not a true reflection of behaviour and this reduces internal validity of the findings as we cant be sure we measured what we set to
• Field experiment

  -          Carried out in natural environment – home or school.

  -          Attempt to improve realism of research.

  -          Used when its particularly important for research to take into account the natural environment.

  -          Researcher manipulates iv and measures dv and attempts to control extraneous variables as much as possible.

  -          Cause and effect can be established, and participants are usually unaware they are participating
• Field experiment

  + strength of field experiment = high levels of ecological validity because they take place in natural environments so the behaviour measure is likely to be representative of behaviour outside of the experiment – which is a strength as we can be more confident generalising results to situations other than the experiment
• Field experiment

  + strength of field experiment = demand characterises are lower because participants don’t know they are taking apart so they can’t guess the researchers aim and amend their behaviour according to it – which increases the internal validity of results as we can be more confident that re dv has measured what it was intended to .
• Field experiment

  A weakness of a field experiment is because of the natural setting it is more time consuming for the researcher – because there could only be a small number of people around at certain times or may not be practical to set the experiment up the amount of time necessary. This is an issues as it may lead to less participants being gathered or it may mean you only get participants who go to the area the research is being carried out in which reduces population validity of the sample meaning it is difficult to generalise the results outside of the population they were found in
• Field experiment

  Weakness of field experiment is that regardless of the researchers attempt it is hard to control all variables in a natural environment as a researcher cannot predict everything that could occur and put controls in place – therefore there could be uncontrollable extraneous variable affecting the dv and the results which reduced are confidence when establishing cause and effect
• Natural experiments

  -          Take advantage of naturally occurring events

  -          Researchers have no direct control over the iv instead making sue of the naturally occurring differences for the independent variable

  -          Participants are not randomly allocated to conditions as the conditions already natural occur – like a group of smokers

  -          Sometimes due to ethical or practical reasons this is the only experiment type suitable – cant ask a group to take up smoking
• Natural experiments

  + strength of the natural experiment= demand characteristics alive because the participants do not know they are taking part so cannot guess the researchers aims nor will they amend their behaviour which increases the internal validity of the results and we can be more confident that our dependent variable has measured what it was intended to
• Natural experiments

  + strength of a natural experiment = they have high levels of ecological validity because it takes place in the natural surroundings of participants meaning that their behaviour measured is likely to be representative of behaviour outside of the experiment which means we can be more confident trivialising the results to situations outside of the experiment
• Natural experiments

  a weakness you have failed experiment is that the likelihood with the desired behaviour intending to test can be limited this is because of research has no control over the situation and they are unable to ensure that the events or behaviour the researcher wants to study will occur this is a weakness as it reduces the available opportunities for researchers to replicate the research and improve plus test for reliability
• Natural experiments

  a weakness of the natural experiment because the events are not planned researchers are unable to control extraneous variables it's impossible for I experimental to predict everything that may occur and put controls in place to deal with them and as such this is a limitation as it means that there could be extraneous variables that the implicating the iv and affecting the dv which produces confidence when establishing cause and effect which also would you sis internal validity
• quasi experiments

  -          Use preexisting independent variables which are usually an individual character trait which does not vary it just exists so participants are not randomly allocated to conditions -conditions could be based on age , gender , phobias

  -          Can be carried out in controlled or natural environments