Almost every experiment has a control group, along with one or more experimental groups. A control group must be included to serve as a baseline comparison in contrast to the experimental group. This allows experimenters to determine whether the treatment (the independent variable) creates significant change. The control group is not given experimental treatment, but may be given a placebo. Any differences between the experimental group and control group can be attributed solely to the experimental variable, as this is meant to be the only distinguishng feature between the experimental and control groups.

Longitudinal studies retest the same subjects multiple times over a long period of time. Some longitudinal studies can span several decades, depending on the type of data being collected. These types of studies are especially popular in the field of developmental psychology.

Applied research is always conducted with the end goal of trying to solve practical problems. The other choices may seek to help solve various issues, but this is not always the case. 

Case studies are rare in psychological research, and are typically used when a subject exhibits a rare and unique symptom pattern. Case studies can also be employed in K-12 school settings to show a child's progress over time in response to various interventions.

Qualitative studies do not measure behavior using numbers. Rather, these studies record behaviors such as dialogue, body language, and other observations. Quantitative studies measure variables numerically in order to conduct statistics on the results. All other answer choices are characteristics that are not confined to either type of study alone.

Doing field work for reserarch can give a much more realistic picture of what would happen in the real world. This helps the researcher to discover the things they could miss in a laboratory setting and spread their net wide. For instance, a researcher may have a hypothesis about how autistic children behave in a classroom setting with other students. By observing this in a natural setting, the research considers all of the real world possibilities of this hypothesis. 

Basic research aims to answer questions that are of concern to a particular field. These questions are more of general interest and can be much more for knowledge's own sake as opposed to means toward a specific end. For instance, trying to answer why the sky is blue doesn't have much practical application, but answers an interesting question.

Applied research aims to apply research in some concrete way. For example, researchers may try to answer specific questions so that they can develop a cure or treatment plan for particular illnesses.

A theory is a statement, concept, or idea that tries to explain some particular phenomenon or pattern in a particular field. A good theory makes a number of claims, all which can be concretely proven through thorough and extensive research that is both valid and reliable.

Validity is when the initial hypothesis is proven to be correct by the research. In other words, the experiment measures what the experimenter had anticipated.

Reliability is when the results of the research can be replicated over and over again consistently. This means that the hypothesis can be tested again in another experiment and still proven to be true.

The main advantage of using a laboratory for research is to provide a highly controlled environment where any interfering factors that may happen in the field can be phased out. This is good for studies that have an extremely narrow focus on some specific element. With regards to psychology, during a child-play experiment in a laboratory a researcher might be trying to see how a child reacts to a particular toy and observe this specific reaction. In the field, however, the child's reaction could be affected by their environment. They could become distracted by their peers and lose focus on the item and thus the researcher can't gather their data accurately.