types of experiment

• labratory experiments- controlled environment(such as noise and temperature), controlled variables, replicated, controlled outcome,
• an advantage for lab experiments is that they can be repeated and controlled, so the results can be more accurate, meaning it has high internal validity. as well as this by keeping all other variables consistent the researchers can be confident in the cause and effect relationship between the changes in the IV
• however lab studies can lack ecological validity and they cannot be applied to real life situations. Task conducted in the lab do not relate to real life complex situations, meaning they lack mundane realism. Demand characteristics are very likely
• field studies carry out experiment in naturalistic settings, this change in location is an attempt to avoid artifical nature of studies. can include shops, schools, homes wherever behaviour is natural
• a weakness of field studies is that there is less control over extraneous variables, making it difficult to determine whether any observed effects were caused by the independent variable or some other factor. This means that field studies may suffer from low internal validity.
• a strength of field studies is that they have higher external validity than laboratory studies because they take place in real world environments which makes them more representative of everyday life. They also tend to have greater ecological validity because participants behave naturally rather than being influenced by demand characteristics.
• natural experiments is when the IV is natural and occurs in the world by itself and does not require the influence of a researcher. the researcher simply records the difference in the DV. natural experiments are usually events that can influence an event, such as political decisions
• strengths of natural experiments is that they have high ecological validity as they occur in real-life contexts. As they are unplanned, they often have high external validity as they are unlikely to be affected by demand characteristics. However, they are rare and therefore hard to find and replicate, meaning they have low reliability
• a weakness of this is the events will happen regardless of the researcher meaning that they have no influence. extraneous variables can't be controlled so researcher can not claim that they have found a cause and effect relationship. replication is also hard as they are rare events so can not be tested for reliability.
• quasi experiments are when pps cannot be randomly assigned between levels of IV because the IV is a characteristic already of the participants such as educational level, gender or mental health
• strengths of quasi experiments is that they have high ecological validity as they occur in real-life contexts. As they are unplanned, they often have high external validity as they are unlikely to be affected by demand characteristics. they are also the only way to assess pre existing characteristics of pps
• weaknesses of quasi experiments is that there may be confounding variables present making it difficult to determine if the IV caused the change in the DV. The lack of random assignment means that groups may differ on other factors besides the IV, leading to differences in the DV. This reduces internal validity and increases the likelihood of type II errors.
• an example of a quasi experiment would be comparing two schools with different teaching styles (IV) and measuring their GCSE results (DV). however, one school might be better resourced than the other, meaning that the difference in GCSE results could be due to the resources available at the school rather than the teaching style.
• correlational studies involve observing how two variables relate to each other without manipulating either variable. correlation coefficients show whether there is a positive or negative association between the two variables. A coefficient of +1 indicates perfect positive correlation while -1 indicates perfect negative correlation. A coefficient of zero shows no correlation
• the strength of correlational studies is that they are easy to conduct as all you need to do is measure both variables. It has high ecological validity as it measures behaviour in real life situations. It also has high external validity as it is likely to generalise to different populations and settings. There is also less risk of demand characteristics as there is no intervention from the researcher
• the main weakness of correlational studies is that they don’t show causality. Correlation doesn’t equal causation. Both variables could be influenced by another variable (third variable problem). Also, correlation doesn’t mean causation as one variable might be causing the other or vice versa. Therefore, we can never say which causes what