A software development company created a new app for fitness, and they want to determine if using the app can lead to weight loss and increased strength in customers. Should they run an observational study or experiment?

Determine whether the study is an observational study or an experiment. Explain.

Researchers conduct a study to determine whether a medication based on fish oil known as omega-3 carboxylic acids is effective in reducing the risk of cardiac events in people already at risk. In the study, 13,078 patients are randomly chosen to receive either omega-3 carboxylic acids or a placebo of corn oil daily. Researchers compare the number of cardiac events of the two groups over similar follow-up periods of time. (Source: American Heart Association)

A regional store manager wants to test whether increasing store hours increases profits, so they randomly select half of their locations to stay open an extra hour later in the evenings and compare profits between stores at the end of the month. They notice that stores open later saw higher profits on average. Is this an experiment or an observational study? Can they determine the extra hours caused the increase in sales? 

A store surveys its target demographic and learns that 86% of people would purchase the product they’ve been heavily advertising. Is this an experiment or an observational study? Can they conclude their current advertising strategy caused the high percentage of interest?

An office manager wants to determine how employees feel about their personal growth and professional achievement in the last quarter. Should they run an observational study or experiment?

"Determine whether the statement is true or false. If it is false, rewrite it as a true statement.

It is impossible to obtain all the census data about the U.S. population."

"Determine whether the data set is a population or a sample. Explain your reasoning.

The salary of each employee of an advertising firm"

"Determine whether the data set is a population or a sample. Explain your reasoning.

A survey of 250 members from an organized union of over 20,000 members"

"Identify the population and the sample. Describe the sample data set.

A survey of 1500 U.S. adults found that 59% have never had a vaccine reaction. (Source: SingleCare)"