Week 6.2-7: Sampling and Quantitative Data Collection

Question 1

Population

Answer 1

P in Pico

The entire gorup of interest based on eligibility criteria

Question 2

Sampling

Answer 2

selection of a portion of the population (a SAMPLE) to represent the entire population

Question 3

Eligibility Criteria

Answer 3

The characteristics that define the population:

Inclusion and Exclusion Criteria

Question 4

What is the most real proxy you can get of something in your study so its highly important to be careful when making it?

Answer 4

The Sample is the most real proxy

Question 5

Sampling Bias

Answer 5

Overrepresenting or Underrepresenting population segment in terms of key characteristics

It is almost always the fault of the researcher and who they have access to (Ex: Picking a convenience sample of college sutdents)

Question 6

Strata

Answer 6

Subpopulations of a population

ex: Male/Female, income, education, comorbidities

Question 7

Target Population

Answer 7

the entire population of interestwe want to generalize

Question 8

Accessible Population

Answer 8

the portion of the target population that is accessible to the researcher, from which a sample is drawn

Question 9

The Goal of Studies from Sampling from the Accessible Population

Answer 9

generalize findings from accessible population to target population

Question 10

How does sampling narrow within the population

Answer 10

Population (All of Life) –> Target Population –> Accessible Population –> Sample

Question 11

What is the biggest and msot consistent threat to internal validity

Answer 11

selection threat

Question 12

Sampling Frame

Answer 12

Through waht resource can you access the target population/accessible population?

Ex: No registrar list of all populations unlike BU - thats why they often use convenience sampling

Question 13

Representative Sample

Answer 13

a sample whose key characteristics closely approximate those of the population

a sampling goal in quantitative research

Question 14

How is a representative sample more easily achieved

Answer 14

probability sampling

homogeneous populations

larger samples achievement through power analysis

Question 15

The goal of a sample is…

Answer 15

to be as reperesentative as possible to the target population

Question 16

The onuse of resposibility for best sampling is on…

Answer 16

the researcher

Question 17

Why is it very important to get a good sample before doing stats?

Answer 17

because the state programs assumed you did best methods and cannot tell you if a sample is not representative

Question 18

Nonprobability Sampling

Answer 18

Does not involve selection of elements at random; it is rarely representative of the population

not great!

convenience sampling, but weakest form of sampling since it under and over represents form a function and behavior of the researcher

Question 19

Probability Sampling

Answer 19

Involves random selection of elements: each element has an equal, independent chance of being selected

Allows researchers to estimate the magnitude of sampling error (difference between population values and sample values)

Question 20

What are the elements mentioned in probability sampling

Answer 20

elements = whatever you are studying (in this case people)

Question 21

What are some types of nonprobability sampling

Answer 21

convenience sampling

quota sampling

consecutive sampling

purposive sampling

Question 22

Convenience Sampling

Answer 22

Nonprobability sampling

selecting the most conveniently available people as participants

cheap and easy but weakest form of sampling

Question 23

Quota Sampling

Answer 23

nonprobability sampling

Identifying population strata and figuring out how many people are needed from each stratum

ex: enroll people until an amount is met - like rolling admission

Question 24

Consequtive Sampling

Answer 24

nonprobability sampling

recruiting ALL people from an accessible population over a specific time interval

Question 25

Purposive Sampling

Answer 25

nonprobability sampling

handpicking sample members

MOSTLY USED IN QUALITATIVE RESEARCH

Question 26

What type of research is purposive sampling used in

Answer 26

qualitative research

Question 27

How may a convenience sample and quota sample differ when recruiting a total population of 20% males and 80% females

Answer 27

the convenience sample will pick whatever they can get so even 5% male and 95% female

quota would keep going until 20% of men chosen and 80% are female

Question 28

Types of Probability Sampling

Answer 28

Simple Random Sampling

Stratified Random Sampling

Systematic Smapling

Question 29

Simple random Sampling

Answer 29

probability sampling

researchers established a SAMPLING FRAME - a list of population elements

then choses elements (people) randomly from the saampling frame

Question 30

Stratified Random Sampling

Answer 30

Probability sampling

the population is first divided into two or more strate from the sampling frame - from which elements are randomly selected

so the elements break into groups of strata and then they select random from those groups

Question 31

Systematic Sampling

Answer 31

Probability sampling

involves the selection of every ‘k’th case from a list, such as every 10th person on a patient list

So when they have the sampling frame / list they chosoe every 10th randomly

Question 32

In order to do probability sampling what is needed first

Answer 32

SAMPLING FRAME

ex: Registrat, tax rolls, voting - but they cannot be biased like the voting or tax rolls too!

Question 33

Sample Size

Answer 33

the number of study participants in the final sample

Question 34

___ ___ adequacy is a key determinant of sample quality in quantitative research

Answer 34

sample size

Question 35

Sample size needs can and should be estimated through __ __

Answer 35

power analysis

Question 36

As the sample size gets smaller…

Answer 36

the risk of “getting it wrong” (Statistical conclusion validity)

too small samples are the number one reason to not get a statistically significant result - type 2 error - results not picked up but are there

Question 37

The ideal sample size is…

Answer 37

large enought to detect differences between two groups

Question 38

Sampling Strategy

Answer 38

1. Define study pop
2. Select inclusion criteria
3. Develop exclusion criteria
4. Design plan to recruit subjects
5. Determine how many subjects are needed
6. Apply the sampling plan/methodology
7. Use strategies to retain subjects

Question 39

Inclusion Criteria

Answer 39

elements must possess characteristics in order to be included in the sample

comes before the exclusion criteria

Question 40

Exclusion Criteria

Answer 40

elements possess characteristics not desired in the study so these elements are not included in the sample

used after the inclusion criteria - so exclude from the crowd

Question 41

Representativeness

Answer 41

How much the sample shares study characteristics with the general population of interest

How close they resemble each other

Generalizability / EXTERNAL VALIDITY

conclusions based on study findings for the “accessible” group are GENERALIZED to the population

Question 42

Critically Appraising Sampling Plans - things to consider

Answer 42

type of sampling approach used (ex: convenience, consequitive, random)

the poopulation and eligibility criteria for sample selection

the sample size, with a rationale

a description of the sample’s main characteristics (ex: age, gender, clinical status, and so on)

*as readers we want to ID these elements

Question 43

What should we assume if we cannot find the sampling method used by authors and also do not see a sampling frame?

Answer 43

90% of the time it means its a convenience sample they hope you did not notice

they would brag about good moethods like RCT and probability sampling methods

Question 44

The author should list sample size analyzed NOT…

Answer 44

size began with before people dropped out