EBP Chapter 6: Sampling

explain response rates

amount of people who answer and return a survey; low rates = low validity

describe the probability and non-probability sampling techniques

-probability: simple random, systematic random, stratified

-non-probability: snowball, convenience/volunteer, judgmental/purposive

what is sampling bias and how does it undermine a researcher's ability to draw conclusions about their research?

it is the possibility that the research may not be accurate?

define response rate

percentage of people who :

-complete a questionnare AND

-return it to researchers

what does it mean if response rate is low?

incorrect conclusions can be made; systematic difference then leads to validity issues!

techniques to increase response rates (4):

-gift incentives

-visually pleasing

-confidentiality/anonymity

-follow-ups

the following are all sampling terminology you need to know (6):

-population

-census

-sampling

-sample

-sampling frame

-representative sample

define population

the entire group of people the researcher desires to learn about

define census

measures each person about whom we wish to know

define sampling

the selection of people to participate in the research project

define sample

smaller group of people who actually participates in the research

define sampling frame

a complete list of all of the people in the population

define representative sample

researchers make inferences from these people to the larger group of people if the small group is almost exactly the same as the large group as a whole

whenever samples are used, the researcher will ______ (always/never) know if the sample is 100% exactly like the population in terms of characteristics

never!

what is the goal of sampling?

to get as close as you can so that the data can be applied to the general population

what are 2 ways to sample?

-probability sampling

-non-probability sampling

define probability sampling

each person in the population has a known chance of being selected to participate in the research

what is required for probability sampling?

HAVE to have a sampling frame!

types of probability sampling (3):

-simple random sampling

-systematic random sampling

-stratified sampling

define simple random sampling

each person in the population has an equal chance to be selected

process of simple random sampling

select people/objects from the sampling frame at random until you reach a desired amount of people/objects in the sample

example of systematic random sampling

-if the list of names on the sampling frame is known to be in a random sequence, every nth name can be selected

-draw a number blindly to tell you where to start on the random list

-population size/sample size you want = #

define stratified sampling

involves drawing separate samples from a set of known subgroups called STRATA rather than sampling from the population as a whole

-this is done to be representative of various variables such as gender, identity, age, ethnicity, geographic region, etc.

probability sampling aka...

representative sampling

probability sampling assumes...

-the existence of one of more sampling frames listing the entire population of interest AND

-everyone has the potential to be sampled

define sampling bias

-occurs when either of these (last card) conditions is not met

-in other words, there is the potential that the sample is not representative of the population

define non-probability sampling

use when probability sample are impossible to get or not necessary

example of when to use non-probability sampling

no sampling frame of the population or the research question does not warrant inferences to be made to greater population

types of non-probability sampling (3):

-snowball sampling

-convenience/volunteer sampling

-judgmental/purposive sampling

define snowball sampling

-rare or difficult to reach population

-one or more individuals from the population are contacted

-these people lead the research to other population members

define convenience/volunteer sampling

research samples whatever individuals are readily available without any attempt to make the sample representative

example of convenience/volunteer sampling

professors who ask their classes to participate in a research project

define purposeful/judgmental sampling

based on:

-researchers knowledge of the population

-purpose of the study

-sample is based on some unique characteristic of the people in the population that is essential to the study