Typically, in a scientific research, researchers are concerned with the specific characteristics of populations of individuals or samples, or they examine external factors that influence populations/sampling. For example; investigation of the effect of weather on the mood of people. Here is the research question; "Does the changes in weather conditions cause changes in people's mood?" Something that can be changed or have different values are called variable. Variable; is characteristic or condition that changes or has different values for different individuals. Variables can be characteristics that differ from one person to another (gender, age, etc.) or environmental factors that affect research such as temperature, time of day, and so on.
It is necessary to make some measurements in order to determine and reveal the differences of the variables in the process of the research. Measurements obtained from variables within each individual sample are called "score" or "raw score". Another name was given to these scores "datum". The complete set of the score is called the “data” or “data set”. Data (plural) are measurements or observations. Datum (singular) is a single measurements or observations and can be called a score or raw score.