CHAPTER 2: TYPES OF STUDIES Flashcards
One of the most
common methods is through the use of
surveys.
can be collected in a variety of ways.
Data
Three of the most common methods of survey
telephone survey
mailed questionnaire
personal interview
4 examples of research sampling
sampling of individuals
sample of institutions
sampling of communities
sampling of non-human populations
3 reasons for sampling
measuring or testing something
not all units in the population can be identified
limitations of resources
5 advantages of sampling
- cheaper
- faster
- better quality of information
- more comprehensive data
- only possible method when teh procedure is destructive
4 considerations for sampling
- objectives of the research
- nature of the problem to be investigated
- time constraints
- availability of financial resources
4 Basic methods of sampling:
random
systematic
stratified
cluster
is a sample in which all members of the
population have an equal chance of being selected.
random sample
is a sample obtained by selecting every kth
member of the population where k is a counting number.
systematic sample
is a sample obtained by dividing the
population into subgroups or strata according to some characteristic relevant to the study.
stratified sample
(There can be several
subgroups.)
stratified sample
Then subjects are selected from each subgroup.
stratified sample
is obtained by dividing the population into
sections or clusters and then selecting one or more clusters and
using all members in the cluster(s) as the members of the
sample.
cluster sample
the researcher uses subjects who are
convenient.
Convenience sample
the respondents decide for themselves if they wish to be included in the sample.
Volunteer sample or self-selected sample
also known as judgement sampling,
Purposive sampling
involves the researcher using their expertise to select a sample that is most useful to the purposes of the research.
Purposive sampling
if the population is hard to access,
snowball sampling can be used to recruit participants via other participants.
Snowball sampling
7 stages of the sampling process
- define the population
- specify the sampling frame
- specify the sampling unit
- select the sampling method
- determine the sample size
- specify the sampling plan
- select the sample
is the difference between the results
obtained from a sample and the results obtained from the
population from which the sample was selected.
Sampling error
occurs when the data are obtained
erroneously or the sample is biased, i.e., nonrepresentative.
non sampling error
it is when the researcher merely observes
what is happening or what has happened in the past and tries to
draw conclusions based on these observations.
observational study
three main types of observational studies.
cross-sectional study.
retrospective study.
longitudinal study.
When all the data are collected at one time, the study is
called
cross-sectional study.
When the data are collected using records obtained from the past, the study is called a
retrospective study
if the data are collected over a period of time, say, past and present, the study is called a
longitudinal study
it is when the researcher manipulates one of the
variables and tries to determine how the manipulation influences
other variables.
experimental study
When random assignment is not possible, researchers use
intact groups
These types of studies are done quite often in education
where already intact groups are available in the form of existing
classrooms.
quasi-experimental study.
in an experimental study is the
one that is being manipulated by the researcher.
independent variable
independent variable is also called the
explanatory variable
The resultant variable is called the
dependent variable
also known as outcome variable, or the response variable
dependent variable
is the variable that is studied to see
if it has changed significantly because of the manipulation
of the independent variable.
dependent/outcome variable
3 Experimental studies advantages:
the researcher can decide how to select subjects
how to assign them to specific groups
control or manipulate the independent variable
3 Experimental studies disadvantages:
they may occur in unnatural settings
the results might not apply to the natural setting
Hawthorne effect
it is when the subjects who knew they were participating in an experiment actually changed their behavior in ways that affected the results of the study.
Hawthorne effect
is one that influences the dependent or
outcome variable but was not separated from the independent
variable.
confounding variable
were the subjects used in the study respond
favorably or show improvement due to the fact that they had been selected for the study. They could also be reacting to clues given unintentionally by the researchers.
Placebo effect
2 Factors that can influence statistical experiments
confounding variable
Placebo effect
To minimize the placebo effect, researchers use what is called
blinding.
the subjects do not know whether they are
receiving an actual treatment or a placebo.
blinding,
Here both the subjects and the
researchers are not told which groups are given the placebos.
double blinding
name of method to minimize variability when they suspect that there might be a difference between two or more blocks.
blocking
When subjects are assigned to groups randomly, and the treatments are assigned randomly, the experiment is said to be a
completely randomized design
Here one subject
is assigned to a treatment group, and another subject is assigned to a control
group. But, before the assignment, subjects are paired according to certain
characteristics.
matched-pair design.
Here the same
experiment is done in another part of the country or in another laboratory.
replication
7 The general guidelines for statisctical study
Formulate the purpose of the study.
Identify the variables for the study.
Define the population.
Decide what sampling method you will use to collect the data.
Collect the data.
Summarize the data and perform any statistical calculations
needed.
Interpret the results.
