Experimental and observational studies

There are two major;types of statisticscal studies ;Experimental study in which all of the factors influencing for the responses are under the direct control of the investigator .

An example of an experimental study is the famouse Hawthorne plant of the western Electric company.The researchers were interested in determining whether increased illumanation would increase the productivity of the assembly line workers.The researchers firsr measured the productivity in the plant.then modified the illumanation in an area of the plant and checked.if the changes in illumanation affected productivity.It turnef out that productivity indeed improved (under the experimental condition).However,the study is heavily criticized today for errors in experimental procedures,specifically fir the lack of a control group and blindness.The hawthorne effect refers to finding that and outcome (in this case,worker productivity) changed due to observation itself.Those in the Hawthorne study became  more productive not because the lighting was changed but becouse they were being observed

Observational study is a type of study in which individuals are observed or certain outcomes are measured.No attempt is made to affect the outcome.

An example of an observational study is one that explores the correlation between smoking and lung cancer.This tyoe of study typically uses a survey to collect observations about the area of interest and then performs statisticscal analysis.In this case,the researchers would collect observations of both smokers and non-smokers, perhaps through a case-control study.and then look for the number of cases of lung cancer in each group