Determine whether the given description corresponds to an observational study or an experiment.

A sample of fish is taken from a lake to measure the effect of pollution from a nearby factory on the fish.

Observational study

Determine whether the given description corresponds to an observational study or an experiment.

A quality control specialist compares the output from a machine with a new lubricant to the output of machines with the old lubricant.

Experiment

The personnel manager at a company wants to investigate job satisfaction among the female employees. One evening after a meeting she talks to all 30 female employees who attended the meeting.

Does this sampling plan result in a random sample? Simple random sample? Explain.

No; no. The sample is not random because not all female employees have the same chance of being selected. Those that didn't attend the meeting have no chance of being selected. It is not a simple random sample because some samples are not possible, such as a sample containing female employees who did not attend the meeting.

Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate.

The sample of spheres categorized from softest to hardest.

Ordinal

Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate.

Salaries of college professors.

Ratio

Identify the type of observational study.

A statistical analyst obtains data about ankle injuries by examining a hospital's records from the past 3 years.

Retrospective

Identify which of these types of sampling is used: random, stratified, systematic, cluster, convenience.

• 49, 34, and 48 students are selected from the Sophomore, Junior, and Senior classes with 496, 348, and 481 students respectively.
• A sample consists of every 49th student from a group of 496 students.

Stratified

Systematic