Flashcards · 4040 · Topic 1

Data and its collection flashcards

26 cards on Topic 1, subtopics 1.1 to 1.5. Pick a subtopic or study them all.

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What are a population and a sampling frame?: The population is the whole group you want information about. The sampling frame is the list the sample is chosen from.
What are the advantages and disadvantages of a census compared with a sample?: A census covers every member, so it has no sampling error. It costs much more time and money and is often impractical for a large population. A sample is cheaper and quicker but has sampling error.
Is a sample automatically inaccurate?: No. A sample has sampling error (chance differences from the population), which is different from bias (a systematic error in the method).
Does a larger sample remove bias?: No. It reduces sampling error only. A biased method stays biased however large the sample is.

What is simple random sampling?: Every member of the population has an equal chance of being chosen, for example by lottery or random numbers. It can still be unrepresentative by chance.
How do you take a systematic sample of 20 students from a school of 800?: List all 800 students. Sampling interval = 800 ÷ 20 = 40. Pick a random start between 1 and 40, then take every 40th student. Risk: a hidden pattern in the list that matches the interval.
A factory has 240 production, 90 sales and 30 admin staff. Find a stratified sample of 36: Sampling fraction = 36 ÷ 360 = 1/10. Production 24, sales 9, admin 3 (total 36). Each stratum's share is then chosen at random within that stratum.
What is quota sampling?: The interviewer fills a fixed quota for each category, choosing who to ask within each group. It is not truly random, so interviewer bias is possible.
What is the difference between cluster and stratified sampling?: Cluster: whole groups are chosen at random and everyone in a chosen cluster is included. Stratified: a random sample is taken from every group, in proportion to its size.
What is opportunity sampling?: Sampling whoever happens to be available. It is quick, but highly unrepresentative.

How do leading or loaded questions cause bias?: The wording pushes a particular answer.
What is non-response bias?: Those who do not respond may differ systematically from those who do.
What is interviewer bias?: The presence or tone of the interviewer affects the answers.
How can an unrepresentative sample cause bias?: For example, surveying only one location or one age group, so some parts of the population are left out.
How can bias in a survey be reduced?: Use a random method from a complete sampling frame, write neutral and clear questions with options that do not overlap, run a pilot survey first, and raise the response rate (for example with a reminder).

What is the difference between a closed and an open question?: Closed has fixed options, open has none. Do not call a question open just because it has a long stem.
What are the advantages and disadvantages of open questions?: Open questions give reasons and unexpected answers. They are slower to answer and must be coded (sorted into categories) before they can be counted. Memory line: closed gives counts, open gives reasons.
What do "exhaustive" and "mutually exclusive" mean for response options?: Exhaustive means nothing is missing; mutually exclusive means nothing overlaps.
What does a pilot survey test?: The pilot tests the questionnaire, not the population. It finds unclear questions, missing options and length problems so they can be fixed before the main survey.
How is a response rate calculated?: Response rate = usable replies ÷ number asked × 100. Example: 150 forms given out, 90 usable ones returned → 60%.
What is a double-barrelled question, and how is it fixed?: A question that joins two ideas with "and", such as "Is the cafeteria cheap and friendly?". Split it into two separate questions.

What is qualitative data?: Data described by category, not number (favourite subject, eye colour).
What is discrete quantitative data?: Data that takes only certain, separate values (number of siblings, goals scored). It is usually countable, but "counted" is a rule of thumb, not the deciding test.
What is continuous quantitative data?: Data that takes any value in a range (height, time, mass). It is usually measured, but that is a heuristic, not the definition.
What is the difference between primary and secondary data?: Primary data is collected by the researcher for their exact need: well matched but more costly. Secondary data was collected by someone else for another purpose (such as census data): cheaper but may not fit exactly.
A time is recorded as 8.6 seconds to 1 decimal place. Between which values does it lie?: 8.55 ≤ t < 8.65. The boundaries sit halfway between neighbouring recorded values.