Question

 

Suppose you wanted to survey the residents of Yorktown to find out about their attitudes toward Mercy College students. Describe how you would try to obtain a random sample from this population. Outline each of the steps required to obtain a random sample. Describe at least one advantage and one disadvantage of this sampling plan. (5 points)

Answer 1

Let's say that the Yorktown has roughly 100,000 residents. These 100,000 residents are our population (N). In order to select a sample (n) of residents from this population of 100,000 residents to find out about their attitudes towards Mercy College Students, we could choose to use a simple random sample.

With simple random sampling, there would an equal chance (probability) that each of the 100,000 residents could be selected for inclusion in our sample. If our desired sample size was around 1000 residents, each of these residents would subsequently be sent a questionnaire to complete (imagining we choose to collect our data using a questionnaire).

To create a simple random sample, there are six steps:

(a) defining the population;

(b) choosing your sample size;

(c) listing the population;

(d) assigning numbers to the units;

(e) finding random numbers; and

(f) selecting your sample.

STEP ONE
Define the population

In our survey, the population is the 100,000 residents at Yorktown. The population is expressed as N. Since we are interested in all of these residents, we can say that our sampling frame is all 100,000 residents.

STEP TWO
Choose your sample size

Let's imagine that we choose a sample size of 1000 residents. The sample is expressed as n. This number was chosen because it reflects the limit of our budget and the time we have to distribute our questionnaire to residents. However, we could have also determined the sample size we needed using a sample size calculation, which is a particularly useful statistical tool. This may have suggested that we needed a larger sample size; perhaps as many as 2000 residents.

STEP THREE
List the population

To select a sample of 1000 residents, we need to identify all 100,000 residents at Yorktown. If you were actually carrying out this research, you would most likely have had to receive permission from the Authorities. You can read about this later in the article under Disadvantages of simple random sampling.

STEP FOUR
Assign numbers to the units

We now need to assign a consecutive number from 1 to N, next to each of the students. In our case, this would mean assigning a consecutive number from 1 to 100,000 (i.e., N = 100,000; the population of residents at Yorktown.

STEP FIVE
Find random numbers

Next, we need a list of random numbers before we can select the sample of 1000 residents from the total list of 100,000 residents. These random numbers can either be found using random number tables or a computer program that generates these numbers for you.

STEP SIX
Select your sample

Finally, we select which of the 100,000 residents will be invited to take part in the research. In this case, this would mean selecting 1000 random numbers from the random number table.

Advantage of simple random sampling:

The aim of the simple random sample is to reduce the potential for human bias in the selection of cases to be included in the sample. As a result, the simple random sample provides us with a sample that is highly representative of the population being studied, assuming that there is limited missing data.

Disadvantage of simple random sampling

A simple random sample can only be carried out if the list of the population is available and complete. Even if a list is readily available, it may be challenging to gain access to that list. The list may be protected by privacy policies or require a lengthy process to attain permissions.