Unit 3: Collecting Data

In a stratified random sample, the population is divided into groups called strata, and then:

The purpose of random assignment in an experiment is to:

An observational study differs from an experiment in that an observational study:

Voluntary response samples are often biased because:

In a double-blind experiment:

Response bias in a survey can occur when:

A blocked experiment differs from a completely randomized experiment because blocks:

A cluster sample differs from a stratified sample in that:

A researcher divides a school into freshmen, sophomores, juniors, and seniors, then randomly selects 25 students from each group. What type of sampling is this?

A survey about exercise habits is conducted by only surveying people leaving a gym. This is an example of what type of bias?

In a well-designed experiment, what is the purpose of random assignment?

Which of the following distinguishes an experiment from an observational study?

A study finds that students who eat breakfast score higher on exams. However, students who eat breakfast also tend to get more sleep. In this case, sleep is a:

In a double-blind experiment, who knows which subjects receive the treatment and which receive the placebo?

In a simple random sample (SRS) of size n from a population of size N:

In an experiment, subjects are first grouped by gender and then randomly assigned to treatments within each group. This technique is called:

An online poll asks visitors to a website to vote on an issue. This is an example of:

Why is replication important in experimental design?

In a matched pairs experiment, each subject receives:

What type of sampling method did the researcher use?

What type of bias is most likely present in this survey?

Why is random assignment important in this experiment?

Is this study an experiment or an observational study?

Which variable is most likely a confounding variable in this study?

What conclusions can be drawn from this study?

Why did the researcher use blocking in this experimental design?

Why was a placebo group included in this study?

A hospital wants to test whether a new drug reduces recovery time. Patients are allowed to choose whether they take the new drug or a standard treatment. Patients who chose the new drug had shorter recovery times. Why can we NOT conclude that the new drug caused shorter recovery times?

A researcher wants to compare three fertilizers on crop yield. She has 30 plots arranged in two rows: 15 on a hillside (more sunlight) and 15 in a valley (less sunlight). She randomly assigns 5 plots in each location to each fertilizer. What is the purpose of this design?

A polling organization calls 1,000 randomly selected landline phone numbers and asks about technology usage. Which of the following is most likely to cause bias in this survey?

A pharmaceutical company tests a new drug by randomly assigning 200 patients to receive either the drug or a placebo. Neither the patients nor the doctors evaluating outcomes know which group each patient is in. Halfway through, researchers notice that the treatment group is older on average than the control group. What is the best explanation?

A school wants to estimate how much time students spend on homework. They randomly select 10 students from each grade level (9th through 12th). This sampling method is: