Whether or not a particular discipline, such as psychology, is a science has more to do with the methods used than with the particular subject area studied. An area of inquiry is a scientific discipline if its investigators use the scientific method—a systematic approach to researching questions and problems through objective and accurate observation, collection and analysis of data, direct experimentation, and replication of these procedures. Scientists emphasize the importance of gathering information carefully and accurately, and researchers strive to remain unbiased when evaluating information, observing phenomena, conducting experiments, and recording procedures and results. Researchers also recognize the value of skepticism and the necessity of having their findings confirmed by other scientists.
Developmental psychology research is the scientific means of acquiring information about groups and individuals regarding various aspects of human development. A developmental psychologist begins a research study after developing ideas from a theory, or an integrated set of statements, that explain various phenomena. Because a theory is too general to test, the investigator devises a hypothesis—a testable prediction—from the theory and tests the hypothesis instead of a general theory. The results of the research study either disprove or do not disprove the hypothesis. If the hypothesis is disproved, it cannot be used to make predictions, and the investigator must question the accuracy of the theory. If the hypothesis is not disproved, the scientist can use it to make predictions about the phenomena that he or she is studying. These predictions may help scientists do one of the following:
- Form explanations of the causes of the phenomena.
- Draw conclusions about how the phenomena will affect groups and individuals.
A goal of developmental research is to discover the developmental similarities, differences, patterns, and trends of the population group that is under investigation. A population is a body of persons having qualities or characteristics in common. Members of a population who participate in a study are referred to as subjects or respondents. When the characteristics of a portion of the population are representative of the characteristics of the entire population, scientists can apply, or generalize, their findings from the sample to the population as a whole. The best and most representative sample is a random sample, in which each member of a population has an equal chance of being chosen as a subject.
In quantitative research, information is collected from respondents (for example, the number of years that they have been in college) and converted into numbers (junior equals 3; senior equals 4). In qualitative research, information collected from respondents takes the form of verbal descriptions or direct observations of events. Although verbal descriptions and observations are useful, many scientists prefer quantitative data for purposes of analysis.
When information is collected through a test, researchers try to ensure that the test is
- Valid: Measures what it purports to measure.
- Reliable: Provides consistent results when administered on different occasions.
To analyze data, scientists use mathematical procedures known as statistics to describe and draw inferences from data. Two types of statistics are most common:
- Inferential: used for making predictions about the population.
- Descriptive: used for describing the characteristics of the population and subjects. Scientists use both types of statistics to draw general conclusions about their population and sample.