Chapter 13

Question 1

What is a population?

Answer 1

the aggregate of persons or
objects that meet a specified set of criteria,
and to whom we wish to generalize results
of a study

Question 2

What is a sample?

Answer 2

a subgroup of the population
Serves as the reference group to estimate characteristics of and to draw conclusions about the population

Question 3

What is a target population?

Answer 3

overall group to which findings will be generalized

Question 4

What is an accessible population?

Answer 4

persons who have an actual chance to be selected, who are availible

Question 5

What is inclusion criteria?

Answer 5

the primary traits of the target and accessible populations that will make someone eligible to be a participant

Question 6

What is exclusion criteria?

Answer 6

factors that would preclude someone from being a subject
- potentially variables that may confound the results or interfere with interpretation of the findings

Question 7

What are the types of probability sampling?

Answer 7

simple random sampling
systematic sampling
stratified random sampling
cluster sampling
disproportional sampling

Question 8

What are the types of nonprobability sampling?

Answer 8

convenience sampling
quota sampling
purposive sampling
snowball sampling
voluntary response sampling

Question 9

Why is sample size essential?

Answer 9

The issue of sample size is an essential one, as it directly affects the statistical power of the study.

Question 10

What is power?

Answer 10

Power is the ability to find significant effects when they exist. It is influenced by several factors, including the variability within the sample, the anticipated magnitude of the effect, and the number of subjects. With a small sample, power tends to be low, and a study may not succeed in demonstrating the desired effects.

Question 11

What is sampling error?

Answer 11

Sampling error is a measure of chance variability between a sample and a population. The term “error” in statistics does not mean a mistake but is another word for unexplained variance.

Question 12

What is sampling bias?

Answer 12

Sampling bias occurs when the individuals selected for a sample overrepresent or underrepresent certain population attributes that are related to the phenomenon under study. Such biases can be conscious or unconscious. Conscious biases occur when a sample is selected purposefully.

Question 13

What is simple random sampling?

Answer 13

Each member of the defined accessible population has an equal chance of being selected.

Question 14

What is systematic sampling?

Answer 14

Persons are randomly chosen from unordered lists using a fixed sampling interval, such as every 10th person. The interval is determined by the desired sample size and the number of persons on the list. As long as lists have no biased order, this is considered a random process.

Question 15

What is stratified random sampling?

Answer 15

A particular sample characteristic is used to partition members of a population into non- overlapping subsets or strata, and random samples are drawn from each stratum based on the proportion of the population within each stratum.
Study of depression as a risk factor for dementia
Proportional sampling for four strata

Question 16

What is cluster sampling?

Answer 16

*With especially large populations, samples are randomly chosen at multiple stages, such as counties, city blocks, households, and individuals.

Question 17

What is area probability sampling?

Answer 17

a type of cluster sampling in which a population is sampled geographically

Question 18

What is random-digital dialing?

Answer 18

a type of cluster sampling involving the generation of random numbers that may be based on lists of landlines or cellphones

Question 19

What is disproportional sampling?

Answer 19

A form of stratified sampling, disproportional sampling is used when certain strata are underrepresented in the population, which leads to their having small representation within the total sample. These strata are oversampled to provide stronger representation, and weights are used to adjust data to correct for this bias.

Question 20

What is convenience sampling?

Answer 20

Also called accidental sampling, subjects are chosen based on their availability. For example, they may be recruited as they enter a clinic, or they may volunteer through advertising.
A practical approach to convenience sampling is consecutive sampling, which involves recruiting all patients who meet the inclusion and exclusion criteria as they become available, often as they enter a clinic for care. The sample is usually defined by a period within which patients become enrolled.

Question 21

What is quota sampling?

Answer 21

A form of stratified sampling that is not random, where subjects are recruited to represent various strata in proportion to their number in the population.

Question 22

What is purposive sampling?

Answer 22

Subjects are hand-picked and invited to participate because of known characteristics.

Question 23

What is snowball sampling?

Answer 23

Small numbers of subjects are purposively recruited, and they help to identify other potential participants through networking. This approach is used when subjects are difficult to identify, especially when dealing with sensitive topics.