Statistics Chapter 1

What is random sampling?

Every person in the population has an equal chance of being selected

What are the advantages of random sampling?

Representative, unbiased

What are the disadvantages of random sampling?

Needs a large sample size, can be expensive and time-consuming

What is stratified sampling?

the size of each strata in the sample is in proportion to the sizes of strata in the population

What are the advantages of stratified sampling?

Representative, good for populations with unequal group sizes

what is systematic sampling?

choosing items in the population at regular intervals

What are the advantages of systematic sampling?

can be carried out by a machine, is evenly sampled

what is a disadvantage of systematic sampling?

not strictly random as some members cannot be chosen

what is cluster sampling?

The population is divided into natural groups (clusters), groups are chosen at random and every member of groups are sampled.

what are the advantages of cluster sampling?

economically efficient, can be representative

what are the disadvantages of cluster sampling?

not representative, high sampling error

What is quota sampling?

Population is grouped by characteristics and a fixed amount is sampled from every group.

What is the method for quota sampling?

Group population by characteristics

▪ Select amount for each group

▪ Obtain sample by finding members of each group until quota is reached.

What are the advantages of quota sampling?

Cheap and quick to use

What are the disadvantages of quota sampling?

Not random- biased

What is opportunity sampling?

Using the people/items that are available at the time.

What are the advantages of opportunity sampling?

Cheap and easy

What are the disadvantages of opportunity sampling?

not random- not everyone has equal chance of being selected

what is judgement sampling?

When the researcher uses their own judgement to select a sample, they think will represent the population.

what are the strengths of judgement sampling?

quick + easy

what are the disadvantages of judgement sampling?

not random- biased and unreliable

what are the assumptions using the petersen capture-recapture method?

Population has not changed

Probability of being caught is equal for all

tags not lost

What is a laboratory experiment?

Researcher has full control over variables- conducted in a lab or similar environment

What are advantages of laboratory experiments?

Easy to replicate, extraneous variables can be controlled

What are the disadvantages of laboratory experiments?

People may behave differently under test conditions- less valid

What are field experiments?

Carried out in the everyday environment- researcher has some control over the variables

What are the strengths of field experiments?

More accurate- reflects real life behaviour

What are the disadvantages of field experiments?

Cannot control extraneous variables, not easy to replicate

What are natural experiments?

Carried out in the everyday environment- researcher has no/very little control over the variables

What are the advantages of natural experiments?

reflects real life behaviour

what are the disadvantages of natural experiments?

difficult to replicate, cannot control extraneous variables

What are features of a good questionnaire?

Easy to understand

Avoids leading questions

Includes non-overlapping, exhaustive option boxes

What are the problems of questionnaires?

Non-response- people do not respond

Sensitive questions

What are the advantages of doing a census?

Unbiased, accurate

What are the disadvantages of doing a census?

Time-consuming, expensive

What are the advantages of doing a sample?

Cheaper, quicker and less data to consider

What are the disadvantages of doing a sample?

may be biased, unrepresentative