A manager at a large manufacturing company wants to conduct

A manager at a large manufacturing company wants to conduct a survey of company workers. The manager wants a simple random sample of 40 workers. Which of the following methods will produce a simple random sample?

Survey the first 40 workers to arrive at the plant in the morning.

Survey every 5th worker entering the plant until 40 workers are surveyed.

Number the workers in the official list of employees. Use a table of random numbers to choose 20 male workers and 20 female workers.

Write down each worker\'s name on a separate slip of paper. Put the papers into a box and randomly choose 40 slips.

Solution

The fourth choice is correct: Write down each worker\'s name on a separate slip of paper. Put the papers into a box and randomly choose 40 slips. Only in this one does each worker have an equal chance of being selected. The first choice is not random: it\'s a convenience sample. The second is a systematic sample. The third introduces bias because we don\'t know the proportion of male vs. female workers. Further, even if it were 50/50, a random sample would not necessarily include those exact proportions.