Question

A. In a pilot study involving 150 agricultural workers in an irrigation project, 40% were found to have active schistosomiasis. In a similar pilot study of 150 agricultural workers not employed on the irrigation project, 38% had active schistosomiasis. If an epidemiologist aims to conduct a larger study to estimate the schistosomiasis risk difference within 5 percentage points of the true value with 95% confidence, how many individuals must be included in each of the two groups? Hint: n = (Z / (2α)^2) * ((P1(1-P1) + P2(1-P2)) / (Absolute precision)^2)

b. Explain the fundamental steps involved in stratified random sampling.

c. Describe the key differences between proportionate stratified sampling and disproportionate stratified sampling in the context of sampling techniques.

d. Please provide a brief explanation of the distinction between experimental and quasi-experimental research designs.

Answer 1

The sampling methods used in the given scenarios are stratified random sampling, cluster sampling, and simple random sampling respectively.

Step-by-step explanation:

To answer the student's specific scenarios and clarify the methodologies used:

• Stratified random sampling is utilized when a soccer coach selects players from different age groups to form a team because the coach is dividing the population into 'strata' based on age and then taking random samples from each stratum.
• Cluster sampling is employed when a pollster interviews all human resource personnel in five different companies, as the companies serve as clusters, and all members within selected clusters are surveyed.
• The educational researcher using a simple random sampling approach selects an equal number of male and female teachers randomly, not considering any hierarchical grouping or ordering within the population.