Question

State which sampling design should be used in the following situations, and justify your reasoning:

i. You need to collect statistics on types of software applications used by employees of a company. Separate lists of employees are available classified by job categories.

ii. Patients arriving at an emergency room facility are to be sampled to study their demographics, type of injury, etc. It is decided to sample 10% of the patients.

iii. An engineering school plans to conduct a mail survey of its alumni who graduated after 1980 to collect data on their current employment status. A complete alphabetical list of the alumni is available.

iv. A national sample of college students is to be taken, but a comprehensive list of all college students doesn't exist. A list of all colleges (private and public) exists. For any particular college, a list of all students can be obtained.

Answer 1

i. since separate lists of employees are available classified by job categories; the appropriate sampling method here would be Stratified sampling. every list classified by job categories will form a stratum and together they will form a strata from which a random sample will be drawn. further , here we see within stratum homogeneity and between strata heterogeneity which is essential for stratified sampling.

ii. since it is decided to sample 10% of the patients; a suitable sampling method would be systematic sampling. we will first select any random no. say 4 which will be our random start and then select every 4th person and so on until 10% of the total patients is covered.

iii. since a complete alphabetical list is available; the most appropriate sampling method here would be simple random sampling which can be done using random no. table or lottery.

iv. here the sampling method suitable will be cluster sampling; every college will form a cluster and for each college its students will form its elements.