Unit 4 Review
Inspectors for a hospital chain with multiple locations randomly select some of their locations for a cleanliness check of their operating rooms. The inspectors check every operating room in the hospitals that were chosen. What type of sample is this?
Cluster random sample
A professor wants to study the effectiveness of a new study tool for a course. There are 150 students registered for the course. The professor assigns each student a number from 1 to 150 and uses a RNG to assign the first 75 students selected to use the new study tool. The remaining 75 subjects are assigned to use the previous study tool. What type of experiment design is this?
Completely randomized
Mr. Thompson runs his own printing and bookbinding business. He suspects that the machine isn't enough glue into the book spines and decides to inspect his most recent order of 70 textbooks to test his theory. He numbers them 01-70 and, using the random digit table printed below, selects a simple random sample of 5 books to check. Which books are in the sample? 85063 55810 10470 08029 30025
06, 35, 58, 10, 47
The library where Kara works is planning to add a maker space where members can share equipment and services to create crafts. Kara randomly selected members from their database, then contacted them to ask what kinds of equipment and services they would be most likely to use. What type of observational study is this?
A sample survey
A large random sample of first-year students at Duke University - a private university in North Carolina - was polled about their overall satisfaction with campus living. To which population can the results of the poll safely be generalized?
All first-year students at Duke University only
According to a study published in the journal PM, ayahuasca - a drink made of Amazonian plants - can help people with depression. The study involved 29 participants who all had depression. Doctors gave each of the participants either ayahuasca or a placebo beverage that looked and tasted similar. Those who drank ayahuasca showed significantly lower levels of depression compared to those who drank the placebo beverage. What type of study is this, and what is the response variable?
An experiment where depression level is the response variable
Angela created an maintains an exercise ap where users log their workouts. She wonders if sending users a daily notification that reminds them to use the app will result in them logging more workouts. She releases an update to her app so that half of users will have daily notifications and the other half won't have daily notifications (randomly determined for each user). After a few weeks, she'll see if one group logs more workouts on average than the other group. What type of study is this, and what is the response variable?
An experiment where the number of workouts is the response variable
An insurance company wants to study whether offering incentives for preventative care reduces overall health care costs. They select an random sample of 200 of their customers. They use a random number generator to select 100 customer account numbers to offer the incentive. The remaining 100 customers are assigned to the control group. What type of experiment design is this?
Completely randomized
Researchers studying meditation contacted over 1,000 randomly selected adults in 10 nations. The results showed that those who meditated on a regular basis were less likely to suffer from stress that adults who meditate less regularly or not at all. Can we conclude that meditated caused the lower stress? Why?
Not necessarily, because this wasn't an experiment
A grocery store wonders if their sales will be better if they play ambient music or no music at all. Each day for 2 months, the manager flips a coin to determine whether or not the store will play music that day. At the end of the 2 months. the manager finds that, on average, sales were significantly better on days where music was playing. What conclusion can they draw from this study?
Playing music caused better sales
A dentist wants to conduct a survey via telephone to determine what percent of all adults in their city floss daily. Which of these is the best example of response bias?
Some people might feel pressured to say they floss daily even though they don't
Katie has 2 types of dog treats - chicken and beef - and she wonders which type her dog prefers. She carries out an experiment where she offers her dog both treats at the same time. For consistency, she always puts the chicken treat in her right hand and the beef treat in her left hand. Her dog chooses the chicken treat in 85 of 100 attempts. Katie concludes that her dog prefers the chicken treats over the beef treats. What is a confounding variable that makes her conclusion inappropriate?
The lack of randomization in each attempt
An education researcher wonders if young students better learn arithmetic facts using physical flashcards or a new online game. The researcher recruits 505050 students for a study. The study allows parents to choose which learning tool they'd like their child to use: flashcards or the online game. Each student takes a pre-test and a post-test, and at the end of the study, students who used flashcards show significantly better outcomes than students who used the online game. The researcher concludes that flashcards were more effective than the online game for this group of students. What is a confounding variable that makes their conclusion inappropriate?
The parents' choice of which learning tool their child uses
A group of librarians is interested in the number of books and other media that patrons check out from their library. They examine the checkout records of 150 randomly selected adult patrons. Identify the population and the sample in this setting.
The population is all adult patrons of the library; the sample is the 150 patrons selected
A pediatrician randomly selected 10 parents of his patients. Then he surveyed the parents about their opinions of different kinds of diapers. Identify the population and sample in this setting.
The population is the parents of the pediatrician's patients; the sample is the 10 parents of patients selected.
A factory overseer selects 40 threaded rods at random from those produced that week at the factory, then she tests their tensile strength. Identify the population and sample in this setting.
The population is threaded rods produced at the factory that week; the sample is the 40 threaded rods selected
Diego read a medical research study about the connection between type 2 diabetes and walnut consumption. The study looked at dietary and disease patterns in a sample of over 30,000 American adults, and it found that those who consumed more walnuts were significantly less likely to have type 2 diabetes. Diego concluded that eating more walnuts would make him less likely to get type 2 diabetes. Why is Diego's conclusion not appropriate?
The study was observational, so he shouldn't make a casual conclusion
A surgeon developed a new procedure for knee replacement surgery. To study its effectiveness, they recruit patients who need knee replacement surgery and are willing to participate in a blind study. The surgeon randomly assigns each volunteer to receive either the new procedure or the standard procedure. After the surgeon performs the procedure, they monitor each patient to see if one group has better results than the other. What does it mean for this experiment to be blind?
The volunteers are unaware of which surgery they receive.
A team of psychologists was curious if omega-3 fatty acid supplements could help treat depression in adolescents. They recruited 50 adolescents with varying levels of depression to participate in an experiment. The researchers randomly assigned each subject to take either an omega-3 supplement or a placebo daily, and they monitored subjects' depression levels throughout the study. What is the main reason for randomly assigning the subjects?
To create groups that are as similar as possible so the main difference between the groups is the treatment
A store prints a request on each receipt asking customers to fill out a satisfaction survey online if they are willing. What type of sample is this?
Voluntary Response Sample
A company makes a bracelet that is designed to repel mosquitos so people don't have to wear bug spray. Researchers at the company are designing an experiment where volunteers will be assigned either the bracelet or bug spray to use at their homes. The researchers want to use a randomized block design. How should the researchers form the blocks?
Volunteers within each block should live in similar environments to each other when it comes to mosquitos
