Sampling

Question 1

What is a population or universe?

Answer 1

Any complete group with common characteristics

Question 2

What is a population element?

Answer 2

Single member of a population

Question 3

What is a census?

Answer 3

Investigation of all individual elements that make up a population

Question 4

What is a sample?

Answer 4

• Subset of the larger population of interest

- This is the subset of group that the researcher will actually study or investigate

Question 5

What is a population frame?

Answer 5

A list of all the elements in the population

Question 6

What is a sample frame?

Answer 6

A list of all the elements in the population from which the sample may be drawn

Question 7

What is sampling frame error?

Answer 7

An error which occurs when certain sample elements are not listed or are not accurately represented in a sampling frame

Question 8

What is a sampling unit?

Answer 8

An element or group of elements subject to selection in the sample

Question 9

What is inclusion/exclusion criteria?

Answer 9

The criteria potential participants must meet in order to be included in the study

Question 10

What are the core statistical concepts?

Answer 10

• Descriptive statistics
• Inferential statistics
• Population parameters
• Sample statistics

Question 11

What are descriptive statistics?

Answer 11

• Describe the data
• Measure of central tendency, frequencies, dispersion
• Trends

Question 12

What are inferential statistics?

Answer 12

• Project characteristics of a sample to an entire population
• Make an inference about a population from a sample
• Used in hypothesis testing

Question 13

What are population parameters?

Answer 13

• Characteristics of the population
• Variable in a population or measure characteristics of the populaiton
• Greek letters as notation
• μ = ∑X/N

Question 14

What are sample statistics?

Answer 14

• Estimates of population parameters
• Variables in a sample or measures computed from sample data
• English letters for notation
• X̅ = ∑X/N

Question 15

What is the cost associated with sampling and the solution to this?

Answer 15

• A loss of information

- To make up for this loss we have to ensure that the sample is representative of the population

Question 16

What does representativeness determine?

Answer 16

The representativeness of the sample determines the extent to which generalisable inferences can be made

Question 17

What does the CLT imply?

Answer 17

• Suggests that the sampling distribution of the sample mean produces a normal curve
• As the sample size increases, the means of random samples taken form the population approach a normal distribution
• This means we have a representative sample - and our sample mean will be within close range of the true population mean

Question 18

What is probability sampling?

Answer 18

Chance of selecting any particular member is known and is equal for all units (probability is non-zero)

Question 19

What methods of probability sampling are there?

Answer 19

• Simple random
• Systematic
• Stratified
• Cluster

Question 20

What is simple random sampling?

Answer 20

A sampling procedure that ensures that each elements in the population will have an equal chance of being included in the sample

Question 21

What is systematic sampling?

Answer 21

Every nth name from a list (sampling frame) will be drawn

Question 22

What is stratified sampling?

Answer 22

• Subsamples are drawn within different strata
• Strata are subgroups of elements that may be expected to have different parameters on a variable of interest
• Each stratum is more or less equal on some characteristic

Question 23

What different types of stratified sampling are there?

Answer 23

• Subjects drawn from each stratum can be either dispropriationate or proportionate to the number of elements in the stratum
  • Proportionate stratified sampling (20% of members from each stratum)
  • Disproportionate stratified sampling (% of members disproportionate across stratum)

Question 24

What is cluster sampling and what is the important aspect of it?

Answer 24

• Purpose is to sample economically while retaining the characteristics of a probability sample
• Primary sampling unit
  
  • No longer the individual elements in the population
  • Instead, a larger cluster of elements located in proximity to on another

Question 25

What is non-probability sampling and when is it useful?

Answer 25

- Chance of selecting any particular member is unknown | - Useful when sampling frame cannot be created

Question 26

What kinds of non-probabilty sampling are there?

Answer 26

* Convenience methods | * Purposive Methods

Question 27

What types of convenience methods of sampling are there?

Answer 27

* Convenience | * Snowball

Question 28

What is convenience sampling?

Answer 28

- The sampling procedure of obtaining the people or units that are most consistently available - Least reliable of all sampling designs in terms of generalisability, but may be the only viable alternative when quick and timely information is needed

Question 29

What is snowball sampling?

Answer 29

- Initial respondents are selected by probability methods | - Additional respondents are obtained form information provided by the initial respondents

Question 30

What types of purposive sampling methods are there?

Answer 30

* Judgement | * Quota

Question 31

What is judgement sampling?

Answer 31

- An experienced individual selects the sample based on his or her judgement about some appropriate characteristics required of the sample member - May curtail generaliablity, but it is the only viable sampling method for obtaining the type of information from specific sub-groups

Question 32

What is quota sampling?

Answer 32

- Ensures that the various subgroups in a population are represented on the pertinent sample characteristics - Are basically stratified samples from which subjects are selected non-randomly and on the basis of convenience - Needed to adequately represent minority groups

Question 33

What are confidence and precision in regard to sampling errors?

Answer 33

- Confidence and precision refer to the extent and degree to which legitimate inferences can be made about a target population from a sample - Confidence and precision will be influenced by sampling errors

Question 34

What do sampling errors do?

Answer 34

- Sampling errors limit the extent of generalisability because they diminish representativeness - Sampling errors can cause differences in the sample statistic and population parameters

Question 35

What types of sampling errors are there?

Answer 35

* Random sampling error | * Non-random or systematic sampling error

Question 36

What are random sampling errors?

Answer 36

- Difference between the sample result and the result of a census conducted using identical procedures - Statistical fluctuation due to chance variations - Large number of untypical subjects - Outliers and extreme values - Inversely related to sample size, thus only way to manage is through large sample

Question 37

In sampling, what are non-random or systematic sampling errors?

Answer 37

- Sampling error not due to chance i.e. biased selection - Non-response error - Pattern of responses are atypical of target population: self-selection bias; social desirability - Study design errors or imperfections in execution - Managed through sampling design

Question 38

In sampling, what kinds of non-random or systematic sampling errors are there?

Answer 38

* Self-selection bias | * Social desirability bias

Question 39

What is self-selection bias?

Answer 39

- The bias that creeps into results when the participants of a study are people who choose to participate - The key component is that research subjects (or organisations) volunteer to take part in the research on their own accord. They are non approached by the researched directly - It’s a bias because a group of people who choose to participate is not the same as a random sample of the population - They may also differ in important ways from those who do not choose to partipcate - They motivations and decision to participate in the study may reflect some inherent bias - This can either lead to the sample not being representative of the population being studies, or exaggerating some particular finding from the study

Question 40

What is social desirability bias?

Answer 40

- The tendency of subjects to attribute to themselves statements which are desirable and reject those which are undesirable - In other words, some people like to portray themselves positively - tending to exaggerate or inflate their strengths and achievements, and often deny or trivialise their deficiencies and failures - Particularly problematic with self-reports of performance - To manage this it is important to collect data from multiple sources of use a scale to measure social desirability