Q.Explain the nature of psychological data.

Psychological data, information relating to people's overt or covert behaviour, subjective experience, and mental processes, differ from the data of the physical sciences in several important ways, and understanding this 'nature' of the data is essential before deciding how to collect or interpret it. The single most important idea is that data are never independent, free-standing facts. They are always tied to a context: the physical or social setting in which the behaviour occurred, the particular people involved, the exact time the behaviour took place, and, just as importantly, the specific method and underlying theory that guided how the data were collected in the first place. A person may behave quite differently when alone than in a group, or at home compared with in an office, and a student who reports behaving one way in an interview may be observed behaving quite differently in the actual situation being asked about; this means data never 'speak for themselves' but must always be interpreted by the researcher and placed carefully within their proper context before they can be said to mean anything at all. Psychologists typically distinguish four broad categories of information collected in psychological studies. Demographic information covers personal background details, name, age, gender, birth order, education, occupation, marital status, and family income. Physical information covers the surrounding ecological and material context, terrain, type of economy, housing conditions, and facilities available at home or school. Physiological data covers measurable bodily signals, height, weight, heart rate, Galvanic Skin Resistance (GSR), Electro-encephalograph (EEG) readings, blood pressure and sleep patterns. Psychological information, finally, covers the discipline's own core subject matter, intelligence, personality, interest, values, creativity, emotion, motivation, psychological disorders, illusions, delusions, and consciousness. Measured from this last category, psychological information tends to be comparatively crude, often captured only as categories, ranks, or scores on a scale, and it is also frequently obtained in non-numerical form, through verbal reports, observation records, personal diaries, field notes and archival material, all of which call for a qualitative rather than a purely statistical style of analysis.