Statistics: Meaning, Scope and Data Collection
What the domain covers
In this domain the exam tests whether you can distinguish the discipline of statistics from statistical data, state its scope and limitations, and choose a defensible method of data collection. Statistics (plural) means numerical facts; statistics (singular) is the science of collecting, organising, analysing and interpreting them. Scope includes descriptive and inferential work in economics, business, biology and government; limitations include misuse, ignorance of context and the fact that statistical results are probabilistic.
Core rules
- Primary data are collected first-hand by the investigator; secondary data were collected by someone else and reused.
- Methods include census and sample surveys, personal interview, telephone/mail/web questionnaire, observation and experimentation.
- A variable is a characteristic that varies: qualitative (sex) or quantitative (income); discrete (counts) or continuous (measurements).
- Published sources include government reports, RBI bulletins and trade journals; check reliability, coverage and definitions before reuse.
Worked example
A student uses deposit figures from an RBI bulletin to study savings behaviour. For the student the data are secondary; for the RBI, which compiled them, they were primary. If the student interviews 50 households personally, those responses are primary for the student.
Traps
Do not label data primary/secondary without stating whose perspective is meant. Do not assume a census is always superior: cost, time and non-response matter. A questionnaire is not automatically reliable; wording and pretest affect validity. Numerical facts alone are not 'statistics' unless context and comparison are given.