Types Of Sampling

Question 1

• The first step in selecting a sample is to define the population to which one wishes to generalized the results of a study

• The sample is drawn from the population

• Data is collected from the sample

• Statistics are used to determine how likely the sample results are reflective of the population

• A number of different strategies can be used to select a sample. Each of the strategies has strengths and weaknesses.

• There are times when the research results from the sample cannot be applied to the population because threats to external validity exist with the study.

• The most important aspect of sampling is that the sample represent the population.

Answer 1

SAMPLING

Question 2

• Each subject in the population has an equal chance of being selected regardless of what other subjects have or will be selected.

• A random number table or computer program is often employed to generate a list of random numbers to use.

• A simple procedure is to place the names from the population is a hat and draw out the number of names one wishes to use for a sample.

Answer 2

SIMPLE RANDOM SAMPLING

Question 3

• A representative number of subjects from various subgroups is randomly selected.

• The subgroups are called strata and the sample drawn from each strata is proportionate to the proportions of the strata in the sample

• E.g. if a population has 100 teachers (50 elementary, 30 secondary and 20 tertiary), then in a sample of 10, 5 should be from the elementary stratum, 3 from secondary stratum and 2 from the tertiary stratum

Answer 3

STRATIFIED RANDOM SAMPLING

Question 4

intact groups, not individuals, are randomly selected.

Any location within which we find an intact group of population members with similar characteristics is a cluster.

Examples of clusters are classrooms, schools, city blocks, hospitals, and department stores.

Answer 4

CLUSTER SAMPLING

Question 5

is done when the researcher is unable to obtain a list of all members of the population.

It is also convenient when the population is very large or spread over a wide geographic area.

For example, instead of randomly selecting from all fifth graders in a large city, you could randomly select fifth-grade classrooms and include all the students in each classroom. usually involves less time and expense and is generally more convenient

Answer 5

Cluster sampling

Question 6

•Subjects are selected because they are easily accessible. This is one of the weakest sampling procedures.

• An example might be surveying students in one’s class.

•Generalization to a population can seldom be made with this procedure.

Answer 6

CONVENIENCE SAMPLING

Question 7

• Subjects are selected because of some characteristic.

Also referred to as judgment sampling and is the process of selecting a sample that is believed to be representativ of a given population.

Sample selection is based on the researcher’s knowledge and experience of the group to be sampled using clear criteria to guide the process.

Answer 7

PURPOSIVE SAMPLING

Question 8

• is an easier procedure than random sampling when you have a large population and the names of the targeted population are available.

• involves selection of every nth (i.e., 5th) subject in the population to be in the sample.

• Suppose you had a list of 10,000 voters in your area and you wished to sample 400 voters for research

• We divide the number in the population (10,000) by the size of the sample we wish to use (400) and we get the interval we need to use when selecting subjects (25).

• In order to select 400 subjects, we need to select every 25th person on the list.

Answer 8

SYSTEMATIC SAMPLING