Question

Suppose you work for Milwaukee County Public Office. The county office on aging is imterested in the perceived needs of older adults in their service area. A telephone survey is planned. A systematic random sample of 25% older adults with birth dates prior yo 1938 is generates from voter registration lists. Describe how this would be done. Discuss the strengths and weaknesses of the external validity of this approach

Answer 1

Systematic Random Sampling is a method to select samples at predefined intervals. The researcher selects the random starting point. Steps to setup a systematic random sample would be :

1) Decide the population with birth dates prior to 1938.

2) Divide the total number of elements in the population by the numer of samples needed

This is the sampling interval.

3) Next, select a starting point randomly.

4) Choose samples at decided interval.

This is how we get our sample.

Strengths of this approach:

1) This approach is cost effective compared to other methods like stratified random sampling which can be expensive.

2) It is more effective than random sampling as it avoids researcher's bias in choice. Only the starting point needs to be collected.

3) Clustered selection removed as the risk of unusually close samples is eliminated.

Weaknesses of this approach:

1) This method assumes that population size is known before but it is not possible in a very large population size to know the total elements before sampling.

2) Data manipulation possible as the samples are predefined and a desired outcome can be achieved with this as a standard pattern may be exhibited.

3) Some researchers prefer that some randomness should be present in the sample.