Experimental methods

• An aim identifies the purpose of the investigation. It is a straightforward expression of what the researcher is trying to find out from conducting an investigation. The aim typically involves the word 'investigate' or 'investigation'
• Methods such as observation and self-repots do their best to observe and record people's behaviour, but do not interfere with it in any way or attempt to manipulate the situation.
• Experiments deliberately set up a situation and then watch and record what happens. In experiments the psychologist first puts forward an alternative of experimental hypothesis and then a null hypothesis
• An alternate or experimental hypothesis: this is the statement they wish to test.
• A hypothesis is a testable prediction about what is expected to happen in an experiment.
• A null hypothesis simply states that the results obtained were due to chance and not the independent variable that the researcher changed or the situation they engineered
• Variables that are manipulated or changed by the psychologist (the cause) are called independent variables
• The thing that changes (the effect) as a result of the independent variable, the variable that is measured by the psychologist is called the independent variable.
• A hypothesis is a precise, testable statement of what the researchers predict will be the outcome of the study. This usually involves proposing a possible relationship between two variables: the independent (what the researcher changes) and the dependent variables (what the research measures)
• The null hypothesis states that there is no relationship between the two variables being studied (one variable does not affect the other). It states that results are due to chance and are not significant in terms of supporting the idea being investigated
• The alternative (experimental) hypothesis states that there is a relationship between the two variables being studies (one variable has an effect on the other). It states results are not due to chance and that they are significant in terms of supporting the theory being investigated
• We can never 100% prove the alternative hypothesis, so what we do instead is see if we can disprove, or reject the null.
• Operational variables (or operationalising definitions) refer to how you will define and measure a specific variable as it is used in your study
• Operationalisation has the advantage that it generally provides a clear and objective definition of even complex variables. It also makes it easier for other researchers to replicate a study and check for reliability - makes research more reliable as otherwise we would not be able to replicate to check findings - also means only one aspect of a variable is being measured
• a directional hypothesis is also known as a one-tailed hypothesis
• One-tailed directional hypotheses predict the nature of the effect of the independent variable on the dependent variable e.g. adults will recall more words than children
• A non-directional hypothesis is also known as a two-tailed hypothesis
• A two-tailed non directional hypothesis predicts that the independent variable will have an effect on the dependent variable., but the direction of the effect is not specified e.g. there will be a difference in how many numbers are correctly recalled by children and adults
• Key features of a lab study:

  1. it takes place in a controlled, artificial setting - behaviour not taking place in environment adapted for
  2. standardised procedures are used
  3. the experimenter will be manipulating at least one independent variable, and measuring at least one dependent variable
  4. therefore, there will be two or more conditions
  5. the participants know that they are in a study, although they may be deceived about its true aims
  6. if an effect is observed - it is because the Iv has changed
• This type of experiment is conducted in a well-controlled environment - not necessarily a lab - and therefore accurate measurements are possible
• The researcher decides where the experiment takes place, at what time, with which participants, in what circumstances and using a standardised procedure
• Strengths:

  1. cause and effect can be established
  2. it is easier to replicate a lab experiment because a standardised procedure is used
  3. all for precise control of extraneous and independent variables - allows a cause and effect relationship to be established
  4. high degree of control - leads to greater accuracy known as reliability
• Weaknesses:

  1. the artificiality of the setting may produce unnatural behaviour that does not reflect real life, i.e. low ecological validity. This means it would not be possible to generalise the findings to a real life setting
  2. demand characteristics - the 'screw you effect' where participants purposefully alter their behaviour or experimenter effects may bias the results and become confounding variables
  3. problems with operationalising variables
• Field experiments are done in the everyday environment (i.e. real life) of the participants. The experimenter still manipulates the independent variable, but in real-life setting - so cannot really control extraneous variables - participants usually unaware
• Strengths of a field experiment:

  1. High ecological validity - results relate to everyday life and can be generalised to other settings
  2. higher mundane realism than a lab study as the experimental situation is less artificial - may lead to higher ecological validity
  3. reduced demand characteristics as the aims of the study are less apparent
  4. reduced chance of participant effects leading to more valid behaviour as participants may not know they are taking part in a study
  5. the experimenter can control the IV to measure the DV
• ecological validity = true to real life
• extraneous variables = what we want to find
• Weaknesses of field experiments

  • Harder to control extraneous variables because the experimenter does not have complete control over all variables, reducing internal validity
  • Risk of demand characteristics as the participant may guess the aim of the study
  • Lack of consent
  • Ethical issues as participants may be unaware they are in a study or deceived, leading to psychological harm or privacy issues
  • Harder to replicate than lab studies, leading to issues with reliability
  • Less control over extraneous variables, making it harder to establish causality
• Field experiments may be harder to replicate than lab studies