Sampling Definitions Stats Flashcards
What does population mean?
The group of people from which information can be gathered for a specific study/ survey
What does census mean?
A survey that collects information from every member of the population
What is a sample survey?
A survey in which only a section of the population is surveyed
What is a sampling unit?
Any unit, e.g: person, household, that has information of interest to the survey
What is a sampling frame?
The collection of all sampling units
What is random sampling?
A survey in which each member of the sampling frame has an equal chance of being surveyed
What is systematic sampling?
A survey in which a rule is used to choose a sample. e.g: Every 10th member is chosen
What is stratified sampling?
Taking a proportional sample from groups of a population that behave differently. e.g: 50 men and 50 women
What is quota sampling?
Asking a number of participants from each group in a population, proportional to the size of that group. This method is used when a sampling frame cannot be achieved.
What is opportunity sampling?
Selecting sampling units as they are available. e.g: asking the first 20 people seen in a street
What are independent events?
Events that do not effect each other’s probabilities. Expressed with P(A n B) = P(A) * P(B)
What does P(A n B) mean? (“and”)
The probability of A and B both happening at the same time. If A and B were mutually exclusive events, P(A and B) = 0
What does P(A U B) mean? (union)
The probability of either A or B happening, or both happening. P(A) + P(B) + P(A and B) = P(A U B)
How to find probability from a histogram?
The area is proportional to the frequency, find the area of the concerned event, and divide it by the total frequency.
What is the addition rule?
P(A U B) = P(A) + P(B) - P(A n B) (The “U” and the “n” are interchangeable)
