Nonprobability Sampling

– any technique in which samples are selected in some way not suggested by probability theory.

Reliance on available subjects

Purposive or judgmental sampling

Snowball sampling

Quota sampling

Reliance on available subjects

Purposive or judgmental sampling

Snowball sampling

Quota sampling

Purposive or Judgmental Sampling

a type of nonprobability sampling in which the units to be observed are selected on the basis of the researcher’s judgment about which ones will be the most useful or representative.

Snowball Sampling

a nonprobability sampling method whereby each person interviewed may be asked to suggest additional people for interviewing.

Quota Sampling

a type of nonprobability sampling in which units are selected into a sample on the basis of pre-specified characteristics, so that the total sample will have the same distribution of characteristics assumed to exist in the population being studied.

A researcher studying college success knows that a particular university’s student body is 40% first years, 25% second years, 20% third years, and 15% fourth years. The researcher selects cases to match this distribution. What kind of nonprobability sampling technique has the researcher used?

Because the researcher is sampling in order to match the population distribution, the quota sampling technique is being used.

Representativeness

the quality of a sample of having the same distribution of characteristics as the population from which it was selected.

Representativeness and Probability of Selection

A sample will be representative of the population from which it is selected if all members of the population have an equal chance of being selected in t

EPSEM

(Equal Probability of Selection Method)

Element

that unit of which a population is composed and which is selected in a sample.

Population

the theoretically specified aggregation of the elements in a study.

Study Population

a sampling method in which each element has an equal chance of selection independent of any other event in the selection process.

Random Selection

each element has an equal chance of selection independent of any other event in the selection process.

Sampling Unit

that element or set of elements considered for selection in some stage of sampling.

Confidence Level

the estimated probability that a population parameter lies within a given confidence interval.

Confidence Interval

the range of values within which a population parameter is estimated to lie.

True or False: Regardless of the sample size, the mean of the sampling distribution will equal the true population mean.

True: Regardless of the sample size, the mean of the sampling distribution will equal the true population mean

To study college performance, a researcher obtains a list of all enrolled students at the university from the Registrar’s Office. This list is called what?

This list would be called the sampling frame. The researcher could then select cases from that list to comprise the sample

Types of Sampling Designs

Simple Random Sampling

Systematic Sampling

Stratified Sampling

Implicit Stratification in Systematic Sampling

Systematic Sampling

Stratified Sampling

Implicit Stratification in Systematic Sampling

Simple Random Sampling

a type of probability sampling in which the units composing a population are assigned numbers. A set of random numbers is generated and the units having those numbers are included in the sample.

Systematic Sampling

a type of probability sampling in which every kth unit in a list is selected for inclusion in the sample.

Sampling Interval

the standard distance between elements selected from a population in the sample.

population size/sample size

population size/sample size

Sampling Ratio

the proportion of elements in the population that are selected to be in a sample.

sample size/population size

sample size/population size

Stratified Sampling

Stratification – the grouping of units composing a population into homogenous groups (strata) before sampling.

Slightly more accurate than simple random sampling.

Slightly more accurate than simple random sampling.

Implicit Stratification in Systematic Sampling

Systematic sampling can, under certain conditions, be more accurate than simple random sampling.

When using systematic sampling, the first unit is selected by __________.

When using systematic sampling, the first unit is selected by random choice.

Cluster Sampling

a multistage sampling in which natural groups are sampled initially with the members of each selected group being sub-sampled afterward.

In samples where all sample elements have the same chance of selection, each is given the same weight. This is called a __________ sample.

In samples where all sample elements have the same chance of selection, each is given the same weight. This is called a self-weighting sample

One of the most visible uses of survey sampling lies in _____.

A. political polling

B. probability sampling

C. core sampling

D. nonprobability sampling

A. political polling

B. probability sampling

C. core sampling

D. nonprobability sampling

Answer: A.

One of the most visible uses of survey sampling lies in political polling.

One of the most visible uses of survey sampling lies in political polling.

_____ sampling occurs when units are selected on the basis of pre-specified characteristics.

A. Snowball

B. Quota

C. Purposive

D. Probability

A. Snowball

B. Quota

C. Purposive

D. Probability

Answer: B.

Quota sampling occurs when the units are selected on the basis of pre-specified characteristics.

Quota sampling occurs when the units are selected on the basis of pre-specified characteristics.

_____ describes a sample whose aggregate characteristics closely approximate the aggregate characteristics of the population.

A. Exclusion

B. Probability sampling

C. EPSEM

D. Representativeness

A. Exclusion

B. Probability sampling

C. EPSEM

D. Representativeness

Answer: D.

Representativeness describes a sample whose aggregate characteristics closely approximate the aggregate characteristics of the population.

Representativeness describes a sample whose aggregate characteristics closely approximate the aggregate characteristics of the population.

A _____ is the list of elements from which a probability sample is selected.

A. confidence level

B. confidence interval

C. sampling frame

D. systematic sample

A. confidence level

B. confidence interval

C. sampling frame

D. systematic sample

Answer: C.

A sampling frame is the list of elements from which a probability sample is selected.

A sampling frame is the list of elements from which a probability sample is selected.

_____ is the general term for samples selected in accord with probability theory.

A. Nonprobability analysis

B. Correlation

C. Probability sampling

A. Nonprobability analysis

B. Correlation

C. Probability sampling

Answer: C.

Probability sampling is the general term for samples selected in accord with probability theory.

Probability sampling is the general term for samples selected in accord with probability theory.

A _____ population is the aggregation of elements from which a sample if actually selected.

A. theoretical

B. small

C. large

D. concept

E. study

A. theoretical

B. small

C. large

D. concept

E. study

Answer: E.

A study population is the aggregation of elements from which a sample if actually selected.

A study population is the aggregation of elements from which a sample if actually selected.

Cluster sampling may be used when it is impossible to compile an exhaustive list of the elements composing the target population.

A. True

B. False

A. True

B. False

Answer: A.

Cluster sampling may be used when it is impossible to compile an exhaustive list of the elements composing the target population

Cluster sampling may be used when it is impossible to compile an exhaustive list of the elements composing the target population