0 / 1.2 pts

An urban planner is researching commute times in the San Francisco Bay Area to find out if commute times have increased. In which of the following situations could the urban planner use a hypothesis test for a population mean? Check all that apply.

A) The urban planner asks a simple random sample of 110 commuters in the San Francisco Bay Area if they believe their commute time has increased in the past year. The urban planner will compute the proportion of commuters who believe their commute time has increased in the past year.

Notice: A) Incorrect. The variable is whether or not commuters believe their commute time has increased in the past year, a yes/no question. This is a categorical variable. With this variable, the urban planner could test a hypothesis about one proportion, but not a hypothesis about a mean.

B) The urban planner collects travel times from a random sample of 125 commuters in the San Francisco Bay Area. A traffic study from last year claimed that the average commute time in the San Francisco Bay Area is 45 minutes. The urban planner will see if there is evidence the average commute time is greater than 45 minutes.

C) The urban planner asks a random sample of 100 commuters in the San Francisco Bay Area to record travel times on a Tuesday morning. One year later, the urban planner asks the same 100 commuters to record travel times on a Tuesday morning. The urban planner will see if the difference in commute times shows an increase.

Notice :C) you are correct that the variable "difference in commute time" for each person is quantitative. This is a matched-pairs situation, so the urban planner can use a hypothesis test for a single mean.