Raccolta dati tramite le osservazioni

In statistical analysis, population characteristics are determined based on the data collected from the sample. 

The observational study is one of the most common methods of data collection. Here, samples are observed, and specific characteristics are measured without modifying the sample. 

Suppose one wants to know how many aircraft land in an airport in a day. To find out, count the number of aircraft landing in the airport. This study did not interfere with or manipulate the planes or the airport. 

Another example is a cohort study that follows up with participants over a long period of time. For example, the Nurses’ Health Survey has studied over 280,000 participants over 40 years. 

This study did not interfere with participants’ lifestyle or working, but made several important observations about their health and work schedules, such as an increase in the risk of some cancer types among obese participants and a link between the late-night work schedules and the likelihood of developing certain chronic diseases.