Selecting Samples
Once you've determined conceptually what you are going to be studying and how to operationalize your topic, You need to determine WHO or WHAT you are going to be observing and HOW these people or things (units) are going to be selected.
Sampling simply refers to the process of selecting who or what you are actually going to make your observations on.
You can sample individuals, if your unit of analysis is individuals -- that is you are studying people.
Or you can sample, say TV shows, if your unit of analysis is TV programs -- that is you studying TV shows.
How you go about sampling items (whether they
be people or objects) is very important, because sampling
decisions greatly influence what you learn about the topic you
are investigating.
I Sampling -- process of selecting who or what you are actually going to make your observations on.
A. Basic Terms
1. Population -- All of the people, objects, or events in a defined class.
It is the entire collection of people, items, or events that the researcher wishes to study.
Population is determined and defined by the researcher.
It is an abstract definition of the
items under investigation.
2. Study Population -- Is the actual set or list of all of the people, objects, or events specified in the population.
It is the actual collection of people, objects,
or events that samples will be taken from.
3. Sampling Unit (Sample) -- The people,
objects, or events actually selected from the study population.
4. Statistic -- Description of the Sample.
a. numerical description (mean, mode, median, standard deviation, etc.)
b. of variables (i.e., age, sex, height, IQ, etc.).
c. calculated from observations on the
people, objects, or events found in the sample.
5. Parameter -- Description of the Population.
a. numerical estimation (mean, mode, median, standard deviation, etc.)
b. of variables (i.e., age, sex, height, IQ, etc.).
c. believed to represent the unobserved Population
d. based upon observations of the people,
objects, or events found in the sample.
B Probability Sampling.
Samples are chosen at random.
Random selection is employed as a means of choosing samples.
Random selection means that every person, object, or event present in the sample frame as an equal chance of being included in the sample.
1. Allows you to make estimates about the entire population based on the results a very few observations.
2. Allows you to calculate how much confidence you can place on your estimate.