Purposive Sampling.Doc
[pic]
UNIVERSITI TEKNOLOGI MARA (UiTM), MALACCA
FACULTY of COMMUNICATION & MEDIA STUDIES
DIPLOMA in COMMUNICATION AND MEDIA
COM 361
COMMUNICATION RESEARCH
ASSIGNMENT TITLE:
Purposive Sampling
PREPARED BY:
|NAME |MATRIX NUMBER |
|MOHAMAD FATIN ANNUAR BIN MOHAMAD KHIR |2009418338 |
GROUP:
DMC5E/MC110 5E
PREPARED FOR:
MISS WAN AZFAROZZA
DATE OF SUBMISSION:
07/07/11
Probability Sampling
A probability sampling method is any method of sampling that utilizes some form of random selection. In order to have a random selection method, you must set up some process or procedure that assures that the different units in your population have equal probabilities of being chosen. Humans have long practiced various forms of random selection, such as picking a name out of a hat, or choosing the short straw. These days, we tend to use computers as the mechanism for generating random numbers as the basis for random selection.
1. Simple random sampling
In a simple random sample ('SRS') of a given size, all such subsets of the frame are given an equal probability. Each element of the frame thus has an equal probability of selection: the frame is not subdivided or partitioned. Furthermore, any given pair of elements has the same chance of selection as any other such pair (and similarly for triples, and so on). This minimizes bias and simplifies analysis of results. In particular, the variance between individual results within the sample is a good indicator of variance in the overall population, which makes it relatively easy to estimate the accuracy of results.
However, SRS can be vulnerable to sampling error because the randomness of the selection may result in a sample that doesn't reflect the makeup of the population. For instance, a simple
UNIVERSITI TEKNOLOGI MARA (UiTM), MALACCA
FACULTY of COMMUNICATION & MEDIA STUDIES
DIPLOMA in COMMUNICATION AND MEDIA
COM 361
COMMUNICATION RESEARCH
ASSIGNMENT TITLE:
Purposive Sampling
PREPARED BY:
|NAME |MATRIX NUMBER |
|MOHAMAD FATIN ANNUAR BIN MOHAMAD KHIR |2009418338 |
GROUP:
DMC5E/MC110 5E
PREPARED FOR:
MISS WAN AZFAROZZA
DATE OF SUBMISSION:
07/07/11
Probability Sampling
A probability sampling method is any method of sampling that utilizes some form of random selection. In order to have a random selection method, you must set up some process or procedure that assures that the different units in your population have equal probabilities of being chosen. Humans have long practiced various forms of random selection, such as picking a name out of a hat, or choosing the short straw. These days, we tend to use computers as the mechanism for generating random numbers as the basis for random selection.
1. Simple random sampling
In a simple random sample ('SRS') of a given size, all such subsets of the frame are given an equal probability. Each element of the frame thus has an equal probability of selection: the frame is not subdivided or partitioned. Furthermore, any given pair of elements has the same chance of selection as any other such pair (and similarly for triples, and so on). This minimizes bias and simplifies analysis of results. In particular, the variance between individual results within the sample is a good indicator of variance in the overall population, which makes it relatively easy to estimate the accuracy of results.
However, SRS can be vulnerable to sampling error because the randomness of the selection may result in a sample that doesn't reflect the makeup of the population. For instance, a simple