Case studies are known to examine one individual with the ability to collect very detailed data. Despite the hope of being able to reveal information that may later be true for many people, the ideas and suggestions collected from observing one individual cannot be applied to a population. We cannot be sure that observed principles in a particular case can apply or be true for a population—it could be "an exception to the rule.” For instance, a case study may examine one male individual who smokes and has lived to 110; however, a mass study could have been released that suggests the average lifespan for male smokers to be less than 85. In this instance, the case study was of an atypical example; therefore, it would not be scientifically sound to theorize that all male smokers should have a similar life expectancy based on the information of one extraordinary case.

Surveys provide the ability to sample multiple cases that require volunteers to self-report their opinions and behaviors. This method permits the statistical analysis of the information collected from a wide variety of participants while also covering a broad base of questioning. Subsequently, surveys are not as keen methods of observation as case studies, naturalistic observation, or counseling. These three methods may require a close engagement with an individual in a particular setting; therefore, they provide an opportunity to collect detailed information about one particular individual as opposed to collecting data on massive populations. 

When testing the effects or the relationship between two factors, in this case coconut milk consumption and intelligence, an experiment requires a control and a treatment (experimental) group. The first is the group without the treatment whereas the second is exposed to the treatment (in this case, coconut milk). The two groups should be compared post-experiment after data analysis in order to understand or observe the effects of the treatment relative to standard conditions (in this case, no coconut milk).

The result Rosenzweig and colleagues noted was that the brain weight of the environmentally enriched rats increased over time relative to the impoverished rats. Taking a closer look, they realized that it was specifically the cerebral cortex that had the most significantly noticeable difference. This experiment marked a cornerstone in the “nature vs. nurture” debate where genes ("nature") are said to be be responsible for the brain's blueprints, but experiences ("nurture") fill in the rest—in this case, development and establishing impressive branched neural connections. In order to make sure, Rosenzweig and colleagues repeated the experiment multiple times prior to publishing. This finding has been extended into observing the importance of nurturing in early childhood. This was true for the young rats—as seen in the experiment—and has been noted for young children as well. 

In a meta-analysis, the statistical or experimental methods of multiple studies are reviewed for common techniques, results, or disagreements. This is done in order to discover new areas of research interest. Most dissertation-level research and some graduate theses include some level of meta-analysis to justify new research studies.

Inter-data reliability is a made up phrase. The other four are all types of reliability tests. Inter-rater reliability checks if independent raters or judges agree on what they are seeing. Test-retest reliability checks if repeated tests or administrations lead to similar scores or results. Inter-item reliability checks that if items in an assessment correlate. Split-half reliability checks if both halves or parts of a test measure the same thing.

Longitudinal research is described as research where the same individuals are studied over a long period of time. This type of research produces useful results, but it is extremely costly and not time effective.

Cross-sectional research involves studying participants of varying age groups and comparing some behavior between those age groups. This approach is cost effective and less time consuming that longitudinal, but is subject to more confounding variables and sampling error. In research studies, the choice is generally between cost and time-efficiency and research validity.

Monozygotic twins share 100% of their DNA. As a result, the higher concordance rates in MZ twins that have a mood disorder means that genetic factors played a role in contrast to environmental factors.

In 1961, Albert Bandura and his colleagues conducted a study in which children were placed at a table with engaging toys while they simultaneously watched an adult interact with a tall inflatable clown toy. Some children watched adults aggressively attack the Bobo doll while others watched adults play quietly with other toys. In the control group, no adult model was present at all. After the children watched the adult model, the experimenter took them to another playroom. The experimenter attempted to frustrate the child by explaining to them that the engaging toys there were only for other children—he or she would have to play with the toys in the experimental playroom instead. Afterwards, researchers observed how many aggressive behaviors the child displayed towards the Bobo doll. When the child had seen an adult model beat up and verbally assault the Bobo doll, the child was much more likely to do it as well. On the other hand, children in the other groups were more likely to non-aggressively play with the other toys in the room.