Samuel Chiltern answered
Laboratory experiments and case studies are both useful tools in the field of psychological research, and neither one should be considered better than the other. It's always a case of choosing the right tool for the job.
I'm going to explain a little more about the strengths and weaknesses of both in the rest of my answer.
Advantages and Disadvantages of Laboratory Experiments
Lab experiments are conducted in fundamentally-artificial environments, in which an attempt is made to eliminate all variables that are not directly under study, and to precisely control the quantity of any variables that remain.
The purpose of a lab experiment is to establish a causal link between a particular combination of a set of controlled variables, and a particular outcome.
The work of E.F. Skinner provides many excellent examples of lab experiments.
By releasing a small amount of food every time a rat turned a lever, Skinner was eventually able to remove the food reward entirely, whilst the rat continued to turn the lever regardless.
This demonstrated a causal link between reward (food) and response (lever turning), and how the rat learned to associate the two.
Lab experiments are great when you want to prove an observable fact, but they are less useful when dealing with more complex issues - such as people's emotions, which cannot be directly observed.
Advantages and Disadvantages of Case Studies
Sigmund Freud is probably the most famous proponent of psychological case studies. Case studies focus on the individual, rather than on people as a group.
The results from a case study cannot be easily generalised to the wider population because they are often specific to the individual in question.
It's possible to conduct an in-depth analysis of a person using a case study, usually taking their family environment and personal history into account. No attempt is made to establish direct causal links, but rather to build up an overall picture of a 'typical' individual suffering with the condition being studied.
Case studies will often be used in therapy, where understanding a person's circumstances is important to the healing process. The key weakness of case studies is that it is hard to apply the findings to the wider population - every person you study could be unique in some way.
I'm going to explain a little more about the strengths and weaknesses of both in the rest of my answer.
Advantages and Disadvantages of Laboratory Experiments
Lab experiments are conducted in fundamentally-artificial environments, in which an attempt is made to eliminate all variables that are not directly under study, and to precisely control the quantity of any variables that remain.
The purpose of a lab experiment is to establish a causal link between a particular combination of a set of controlled variables, and a particular outcome.
The work of E.F. Skinner provides many excellent examples of lab experiments.
By releasing a small amount of food every time a rat turned a lever, Skinner was eventually able to remove the food reward entirely, whilst the rat continued to turn the lever regardless.
This demonstrated a causal link between reward (food) and response (lever turning), and how the rat learned to associate the two.
Lab experiments are great when you want to prove an observable fact, but they are less useful when dealing with more complex issues - such as people's emotions, which cannot be directly observed.
Advantages and Disadvantages of Case Studies
Sigmund Freud is probably the most famous proponent of psychological case studies. Case studies focus on the individual, rather than on people as a group.
The results from a case study cannot be easily generalised to the wider population because they are often specific to the individual in question.
It's possible to conduct an in-depth analysis of a person using a case study, usually taking their family environment and personal history into account. No attempt is made to establish direct causal links, but rather to build up an overall picture of a 'typical' individual suffering with the condition being studied.
Case studies will often be used in therapy, where understanding a person's circumstances is important to the healing process. The key weakness of case studies is that it is hard to apply the findings to the wider population - every person you study could be unique in some way.
