Non-Experimental Design
Studies using descriptive design do not include a control group for comparison.
Not all research is about measuring the effects of an intervention on one group compared to a group that did not receive the intervention. There is another class of quantitative research design called non-experimental research. These research designs can be used to show relationships between variables (correlational design). Non-experimental research can also be used to study he existence or incidence of a phenomenon (descriptive design). Note that in a non-experimental design, the independent variable is not controlled.
Correlational retrospective design. Research studies in this category examine how an event in the past may have an effect in the present, for example, presence of cancer and pulmonary disease rates among residents of New York City after the 9/11 bombings.
Correlational prospective design. In a prospective design, researchers believe that a phenomenon may have a future effect on the population of interest. For example, is the existence of lead-based paint in the home correlated to lower education scores? Newborns living in homes with lead-based paint would be followed by the researches and tested on some regular basis to compare test scores.
Descriptive correlational studies demonstrate the relationship among variables without going as far as showing cause and effect. Prevalence and incidence studies are examples of this type of research. In epidemiology, a prevalence study is used to study the saturation of a condition whereas an incidence study is used to study the rate of new cases in the population.
Statistical analysis
Statistical measures of correlation will depend on the data type. Incidence and prevalence are measured by a defined formula for rate.
Strengths and limitations
Non-experimental research lacks the reliability and validity of quasi-experimental and experimental research designs. However, findings from non-experimental research is the first step in determining whether an experimental design is called for.