experimental method & aims -> experimental design

what is a lab experiment?

A lab experiment is a controlled study conducted in a structured environment where researchers manipulate variables to observe their effects on a particular outcome.

advantages of lab experiments

include high control over variables, replicability, and the ability to establish cause-and-effect relationships.

disadvantages of lab experiments

may include lack of ecological validity as ppts may behave unnaturally, low mundane realism and potential for participant bias.

what is a field experiment?

A field experiment is a study conducted in a natural setting where researchers manipulate one or more independent variables to observe their effects on a dependent variable

advantages of field experiments?

Field experiments offer high ecological validity, natural behaviour observation, and the ability to study real-world phenomena in context.

disadvantages of field experiments?

Field experiments may have lower control over extraneous variables which may distort findings - lowers internal validity and challenges in replicability.

what is a natural experiment

A natural experiment occurs when researchers observe the effects of naturally occurring events or conditions on a dependent variable, without direct manipulation of independent variables.

what is a quasi experiment?

this is an experiment where the independent variable is based on an existing difference - for example age or gender. the researcher is unable to manipulate this variable, making it different from a true experiment.

advantages of natural/quasi experiments

Natural and quasi experiments allow researchers to study real-world settings and conditions with no involvement, enhancing external validity. They also often require fewer ethical considerations compared to true experiments. they also are more cost and time-efficient due to lack of manipulation of variables

disadvantages of natural/quasi experiments?

Natural and quasi experiments may have lower internal validity due to extraneous variables making it difficult to establish cause-and-effect relationships. Replication can be challenging so reliability of results cannot be checked.

what is an aim?

An aim is a statement that outlines the purpose or goal of a research study, indicating what the researcher intends to achieve through the investigation.

what is a hypothesis and what are the three types?

A hypothesis is a testable prediction made at the start of the study about the relationship between variables. The three types of hypotheses are null hypothesis (states there is no difference/correlation) non-directional hypothesis (simply states there will be a difference/correlation and is used when previous research is inconclusive or non-existent), and directional hypothesis (states the type of correlation/difference and is used when there is conclusive previous research).

what are the five types of sampling and how can they be done

random sampling - list of everyone in the target population and random selection via lottery method

systematic - sampling frame list is produced and ordered and every nth person in target population is chosen - starts from random place to reduce bias

stratified - strata identified and proportions are worked out in population, random sampling of people from each strata

opportunity - any ppts available at the time

volunteer - advertise the study online, posters and ppts step forward to take part

advantages and disadvantages of random sampling

potentially unbiased as all members have equal chance of selection and extraneous variables should be equally divided

time consuming and difficult to make a list of everyone in the population and contact them all, also probabilities make it hard to obtain diverse sample

advantages and disadvantages of opportunity sampling

most convenient method as it reduces costs and time

sample is not likely to be representative of target population as all from a specific area, research bias as they have a choice of who to pick and may avoid people

advantages and disadvantages of stratified sampling

produces most representative sample due to sample being proportionate of subgroups in the population and still chosen randomly

very time consuming and never fully perfect division of groups

advantages and disadvantages of systematic sampling

unbiased as ppts are selected with an objective system and researcher has no control

not truly random unless starting point in list is randomly selected

advantages and disadvantages of volunteer sampling

minimal input from researcher so less time-consuming

sample may have volunteer bias as people who volunteer may be more confident/interested in the study

what are pilot studies and why are they used?

small-scale trial run of an investigation which involves a handful of ppts and checks that the procedure runs smoothly with any flaws being changed before the real study

in questionnaires/interviews it ensures that all questions are clear

what are single-blind and double-blind procedures?

single-blind is when the ppt does not know the aim, procedures or conditions of the experiment to reduce demand characteristics

double-blind is when the ppt and researcher do not know the aim, procedures or conditions of the experiment to reduce demand characteristics and investigator effects

what is independent measures design and its pros and cons

this is when separate ppts are used per condition

pros - order effects are not an issue, ppts are less likely to guess the aim of the study so less demand characteristics

cons - ppts in different groups are not the same so ppt variables may affect DV and so low internal validity, also less economical as twice as many ppts needed

you can limit the cons by using random allocation which evenly distributes characteristics or match the ppts on variables that are relevant in the study

what is repeated measures design and its pros and cons

same group of people is used for both conditions

pros - ppts variables are controlled so higher validity, fewer ppts are needed so less time/money and effort spent

cons - order effects may influence, ppts may work out aim of the experiment so demand characteristics

limit the cons by using counterbalancing - half ppts take part in A then B and the other do it the other way round

what is matched pairs and its pros and cons

testing separate groups of people but they are matched with member from the other group in a variable such as age, sex, social background

pros - controls some ppt variables, no order effects or demand characteristics as only one condition done

cons - all ppts variables are never fully matched and it can be very time-consuming and expensive

limit cons by restricting the number of variables to match to save time and a pilot study can be done to indicate what key variables should be matched