Study designs are the framework for collecting and analyzing data in a particular study. They can be either descriptive or analytical. A descriptive study describes one or more characteristics of a group, for example, the height of an orange tree or what are the personality traits of a successful industrialist. It is concerned with the question – what and not – why. An analytical study establishes causal relationships among the variables and tests a hypothesis. Analytical studies can be further divided into observational and experimental studies. Observational studies describe how exposure and outcome occur naturally and measure variables of interest without influencing the response. For example, comparing the yield of oranges from two farms with different soil characteristics. This type of study would not manipulate soil or its properties. In contrast, the experimental study actively manipulates the independent variables and measures the outcome or dependent variable. So researchers go back to the farms and see if suitable fertilizers can bring statistically significant improvements in the yield of oranges.