Exam 2 Quantitative Sampling

Question 1

Population

Answer 1

group meeting a specific description

Question 2

Target population

Answer 2

everyone who meets the criteria (very specific criteria for study)

Question 3

accessible population

Answer 3

those who meet the criteria and who can be accessed by the researcher (who researcher has access to)

Question 4

Sample

Answer 4

selected portion of group you are studying

-small, specifically selected to be in study

Question 5

Elements

Answer 5

individual or basic units to be studied

Question 6

subjects/participants

Answer 6

human elements to be studied

Question 7

Sampling plan

Answer 7

how you will select the sample (number, eligibility, process) written description

Question 8

What is representativeness?

Answer 8

the sample looks enough like the population to be able to GENERALIZE the sample findings to others in the population

Question 9

How must the sample similar to the population

Answer 9

on important characteristics

Question 10

Inclusion criteria

Answer 10

characteristics that the subject MUST possess to be in the study.

Based on notable characteristics of the target population

Question 11

Exclusion criteria

Answer 11

characteristics that the subject MUST NOT possess

reduces questions about impact of extraneous variables on the results

Question 12

sampling bias

Answer 12

over or under selection of subjects on any of the significant variables

Question 13

sampling error

Answer 13

errors made in the conclusions because of sampling bias

Question 14

Clinically relevant findings

Answer 14

Overall picture must be one closely resembling

Question 15

Probability sampling

Answer 15

Every element(person) in the accessible population has an equal chance of being selected for inclusion in the study

Question 16

3 conditions:

Answer 16

accessible population must be identifiable (must be able to make a list)

All elements in the accessible population must be listed (sampling frame)

Elements are chosen by random selection

Question 17

Selection method is determined by:

Answer 17

research purpose, question, and design

Question 18

Types:

Answer 18

simple, stratified, cluster, and systematic random sampling

Question 19

Randomization

Answer 19

outcome of random sampling methods

Question 20

What does randomization reduce threat of?

Answer 20

selection bias

Question 21

Less selection bias

Answer 21

ensures a greater likeness between the sample and the target population on the focal characteristics

Question 22

Common methods:

Answer 22

• Draw names out of a hat
• Use a table of random numbers
• Flip a coin-heads in, tails out
• Throw dice-anyone getting an even number is in, odd number is out

Question 23

Simple random sampling

Answer 23

everyone in the accessible population has an equal chance for inclusion

Question 24

process:

Answer 24

-get a list of the accessible population
-assign everyone on the list a number
-randomly select from the list
…whatever it takes to remove brain’s ability to pick

Question 25

Difficult?

Answer 25

if it's a large group, or when one cannot make a sampling frame -to use when one does not know who will be admitted to the unit/hospital/etc meeting the focal characteristics

Question 26

stratified random sampling

Answer 26

select the relevant strata (must be mutually exclusive) -divide the population into subgroups or strata based on some important feature. -decide on how many from each strata -use random sampling to select that number from each strata

Question 27

Difficult?

Answer 27

when accessible population for one strata makes it small or difficult to find

Question 28

Cluster or multistage sampling

Answer 28

clusters narrow down large unwieldy population (Still RANDOM) - Identify important characteristics - look for logical subsets (clusters) of the large population - randomly select your clusters and sub-clusters - randomly select subjects from you clusters

Question 29

systematic sampling

Answer 29

create a list of the accessible population -divide the number of people available by the number of subjects needed to get 'k' example: 500 people/50 needed=10 -draws every 'kth' element example: the above answer of 10 means every 10th person on the list -randomly pick a starting point on your list\ -select every kth person (10th person) until you have your sample.

Question 30

nonprobability sampling

Answer 30

less likely to give you a representative sample | -increased seelction bias

Question 31

when use nonprobability?

Answer 31

when sampling frame cannot be determined

Question 32

types:

Answer 32

convenience, quota, purposive or judgement, snowball, theoretical, expert

Question 33

Convenience sampling

Answer 33

Use any subjects - whatever is available to you - volunteers ex: mall surveyors

Question 34

Convenience sampling: control sampling bias

Answer 34

collecting data on subject characteristics and then making comparisons of those characteristics

Question 35

Quota sampling

Answer 35

- similar to stratified random sampling WITHOUT the random selection steps - decide on variables of interest - decide on the strata to select from - conveniently select from each strata (instead of randomly select)

Question 36

Purposive sampling

Answer 36

- base selection on specific criteria | - inclusion relies on researcher's judgment

Question 37

When is it used?

Answer 37

More often used in qualitative than quantitative designs but may be used in quantitative descriptive studies

Question 38

Snowball sampling

Answer 38

A type of purposive sampling

Question 39

How are subjects obtained?

Answer 39

By referral

Question 40

How is this useful?

Answer 40

Helps to obtain key people or those who might be difficult to find under normal circumstances

Question 41

Theoretical sampling

Answer 41

Used mostly when trying to develop an explanation of a phenomena

Question 42

Two step process

Answer 42

- Collect data - develop initial explanation (theory) - purposefully identify additional subjects to determine if the explanation (theory) continues to hold up

Question 43

Expert sampling

Answer 43

Use when looking for consensus on an issue

Question 44

When to use?

Answer 44

Creating research tools It helps measure content validity

Question 45

Sample size

Answer 45

Samples that are homogeneous (similar) on the desired characteristic do not need to be as large as samples that are heterogeneous (dissimilar) on the desired characteristic.

Question 46

How does reliability/validity effect sample size

Answer 46

The more reliable and valid the tools, the smaller the sample size needed

Question 47

General rules of thumb for sample size:

Answer 47

Minimum of 30 for one group study - if doing group comparisons, need at least 30 in each group - if more than one I.V., need at least 10 for each I.V.

Question 48

Also need to consider for sample size:

Answer 48

Refusal rate since not everyone will want to participate - consider your likely "drop out" or attrition rate - consider "power" of your study

Question 49

Statistical power

Answer 49

looks at your assurance that you are correct in rejecting the null hypothesis - need to consider your alpha (significance lvl), your effect size, and desired power level - if you set your alpha at .05, you are looking for a 95% chance of correctly rejecting the null hypothesis - must decide if you think the I.V. will have a large, medium, or small impact or effect on the D.V. - generally wish a power level of at least .8 - use your alpha, effect size, and desired power to calculate the number of subjects you need for each individual statistical procedure used in the study

Question 50

Recruitment and retention

Answer 50

IRB approval required before approaching any potential subject

Question 51

How can you recruit?

Answer 51

By using personal contact on the unit, contact manager or staff member on the unit, flyers, ads on radio or TV...etc...

Question 52

Requirements for recruitment

Answer 52

All printed documents must be at maximum of 5th grade level in appropriate language - incentives should not be bribes - determine who meets likely the criteria - be professional, personable, and patient - explain exactly how they will participate such as in person, survey monkey, mail in responses, etc... - provide for informed consent - have informed consent form signed if needed

Question 53

Do you always need a SIGNED informed consent form?

Answer 53

NO

Question 54

Informed consent must include:

Answer 54

- title of study - invitation to participate - basis of subject selection - purpose of study - explanation of procedures - benefits and risks - alternatives to participation - financial obligations - confidentiality assurances - HIPAA disclosure of how their data will be protected - subject withdrawal procedures - offer to answer questions with contact information provided - consent statement - identification of researchers - signature and date, if required

Question 55

Who are the Vulnerable Populations?

Answer 55

- Pregnant women - Fetuses - Children - Elderly - Mentally challenged - Prisoners - Other marginalized individuals based on socioeconomics, ethnicity, gender, education, etc.