Sampling

Question 1

target population (reference population):

Answer 1

refers to the group of individuals to which results of the study are applied to; who we are going to study

Question 2

population:

Answer 2

the general group of people from whom information is needed

Question 3

accessible population

Answer 3

the actual population of subjects available to be chosen for a study. This group is usually a nonrandom subset of the target population.

Question 4

the cases included in the study are the “____”

Answer 4

sample

Question 5

sampling bias

Answer 5

bias that occurs when individuals who are selected for a sample over-represent or underrepresent the underlying population characteristics

Question 6

sample:

Answer 6

a collection of subjects (a noun)

Question 7

simple random sample:

Answer 7

A probabilistic sampling method in which each potential subject has an equal chance of being selected

Question 8

inclusion criteria:

Answer 8

A list of specific attributes that will make an individual (or a unit of analysis such as an organization) eligible for participation in a specific study.

Question 9

exclusion criteria:

Answer 9

A list of characteristics that may influence, or “confound,” the outcomes of a study; researchers use these criteria to eliminate individuals (or units of analysis such as an organization) with these characteristics as subjects in a study

Question 10

sampling frame:

Answer 10

A list of potential subjects obtained from various public or private sources

Question 11

extraneous variables:

Answer 11

Individual, organizational, or environmental characteristics other than the factor of interest (i.e., test, predictor, intervention) that may influence the outcome of a study

Question 12

sampling:

Answer 12

the method for selecting individuals for a study, also called “selection”

Question 13

probabilistic sampling:

Answer 13

Methods for choosing subjects that use a random selection process to increase the chance of obtaining a sample that accurately represents the population from which it is drawn

Question 14

nonprobabilistic sampling:

Answer 14

Methods for choosing subjects that do not use a random selection process; as a result, the sample may not represent accurately the population from which it is drawn.

Question 15

cluster sampling:

Answer 15

A form of probability sampling in which large subgroups (clusters) are randomly selected first, and then smaller units from these clusters are successively chosen; also called multistage sampling.

Question 16

convenience sampling:

Answer 16

A nonprobability sampling procedure, involving selection of the most available subjects for a study

Question 17

purposive sampling:

Answer 17

A nonprobability sample in which subjects are specifically selected by the researcher on the basis of subjective judgment that they will be the most representative

Question 18

snowball sampling:

Answer 18

A nonprobability sampling method in which subjects are successively recruited by referrals from other subjects.

Question 19

stratified random sampling:

Answer 19

A probabilistic sampling method in which subgroups of a population are identified and randomly selected to ensure their inclusion in a study

Question 20

systematic sampling:

Answer 20

A probabilistic sampling method in which the first subject is randomly selected from a group organized according to a know identifier (such as birth date) and then all remaining subjects are chosen based on their numerical distance from the first individual.

Question 21

assignment:

Answer 21

putting subjects into groups, also called “allocation”

Question 22

block assignment

Answer 22

An assignment method in which the number of individuals in each group is predetermined; investigators randomly assign subjects to one group at a time until each quota is met.

Question 23

masked (blinded):

Answer 23

(1) In diagnostic test and clinical measure papers, the lack of knowledge about previous test/measure results; (2) in prognostic factor papers, the lack of knowledge about exposure status; and (3) in intervention papers, the lack of knowledge about to which group a subject has been assigned

Question 24

matched assignment:

Answer 24

An assignment method in which subjects are first divided into subgroups based on a specific characteristic such as age, gender, and so forth; members of each subgroup are then randomly assigned to each group in the study to balance the characteristics across the groups.

Question 25

random assignment by individual:

Answer 25

An assignment method in which each subject is randomly allocated to a group based on which side of a coin lands upright or which number is pulled from a hat.

Question 26

systematic assignment:

Answer 26

An assignment method in which subjects count off the group numbers until everyone is assigned

Question 27

primary data:

Answer 27

Data collected in real time from subjects in a study; used in prospective research designs

Question 28

secondary data:

Answer 28

Data that have been collected previously by others for non-research purposes that are used by investigators to answer a research question; used in retrospective research designs.

Question 29

sampling error:

Answer 29

The difference between an observed statistic from a sample and the population parameter

Question 30

type II error:

Answer 30

Failure to reject the null hypothesis, avoidable.

Question 31

power:

Answer 31

The ability of a statistical test to find a significant difference that really does exist; the probability that a test will lead to rejection of the null hypothesis.

Question 32

subjects:

Answer 32

the term used for people in a research study

Question 33

cases:

Answer 33

the term used for records

Question 34

specimen:

Answer 34

the term used in inanimate objects

Question 35

subjects are identified as detailed as needed to meet the _____ of the study

Answer 35

objective

Question 36

inclusion criteria are used to identify the desired ______, examples are ___________________.

Answer 36

characteristics; age, occupation, dx, gender, etc

Question 37

exclusion criteria are used to ______ persons with characteristics or complications that the researcher does not want to study; examples are ____

Answer 37

eliminate; other conditions, mental problems, age, gender, etc

Question 38

Once a population with the desired _____ factors is identified, the researcher must determine an ______ population from which subjects may realistically be recruited.

Answer 38

inclusion, accessible

Question 39

After identifying the population what 3 things need to be done?

Answer 39

1. recruit the subject
2. review for exclusion factors
3. provide informed consent to participate

Question 40

Once the subject agrees to participate what happens next?

Answer 40

they are assigned to a study group

Question 41

The method of assignment is critical in determining the ______ of a research study

Answer 41

rigor (control)

Question 42

What type of sampling techniques uses random selection to assign to groups? What type of rigor does it give the study?

Answer 42

probabilistic, higher level of rigor

Question 43

When randomization is not possible what type of sampling is done? What type of rigor is indicated?

Answer 43

nonprobabilistic, lower rigor

Question 44

If assignment methods are weak, the critical review language will say it is a “_________”

Answer 44

threat to validity

Question 45

Is a larger sample size always better?

Answer 45

no

Question 46

______ has given guidelines to the number of subjects needed to meet the researcher selected significance level.

Answer 46

statistical analysis

Question 47

_________ is the term given to a statistical formula that considers sample size, significance, and error level; normally a researcher proposes this.

Answer 47

power analysis

Question 48

A good rule of thumb is that for every variable being analyzed, a sample needs ____ subjects

Answer 48

15-20

Question 49

Type I error

Answer 49

Incorrectly reject the null hypothesis