Random assignment
A local store is conducting an experiment to determine if customers spend more money when they hear rock music playing while shopping. The manager decides to play music for customers only on Mondays because he's always off on that day.
No random assignment
A beverage company wanted to see if people in the United States liked their new logo. Which choice best represents a population?
Every person in the United States.
True or False: You want to see how many students take the bus home from school. You go to the bus stop and ask students how they get home everyday. This is a good, representation of the population.
False
Gavin is interested in cars. Which of these facts can he determine by conducting a survey in his town?
A drug company draws a random sample of 100 cancer patients from a population list of 1000 cancer patients and randomly places 50 of these patients to receive a new drug and the other 50 to a control group.
both a random selection and a random assignment.
A musician wanted to see what people who bought his last album thought about the songs. Which choice best represents a sample? .
A selection of 3,294 people who bought the album.
A local store is conducting an experiment to determine if customers spend more money when they hear rock music playing while shopping. The manager decides to play music for customers only on Mondays because he's always off on that day.
No random selection
A study investigated the relationship between a subject's heart rate and the frequency at which the subject stepped up and down on steps. There were 3 rates of stepping and 2 different step heights. A subject performed the activity by stepping at one of the 3 stepping rates and at one of the 2 possible heights for three minutes. The subject's heart rate was then measured and recorded.
How many treatments are in the experiment?
6
Which is NOT part of the process of random assignment?
A gaming website wanted to find out which console its visitors owned. Which choice best represents a population?
All of the website visitors.
Which is a part of the process of random selection?
What is the purpose of an experimental study design?
To investigate cause-and-effect relationships between variables.
Researchers are testing a new medication to treat eczema. From a randomly selected group of 100 patients with eczema, they give the new medication to the 50 patients with the most severe and a placebo to the other 50 patients.
Which of the following BEST describes how the assignment process could impact the conclusion of the study?
Random assignment was not used. Because the patients with the most severe eczema received the treatment, it will be difficult to determine whether differences in the two groups are due to the treatment.
Before a nation-wide election, a polling place was trying to see who would win. Which choice best represents a sample?
A selection of voters of different ages.
A drug company draws a random sample of 100 cancer patients from a population list of 1000 cancer patients and randomly places 50 of these patients to receive a new drug and the other 50 to a control group.
both a random selection and a random assignment.
A drug manufacturer is interested in comparing three types of muscle relaxers. The manufacturer wants to determine if one type is better than the other types in terms of improvement in mobility. Three different groups of 50 patients participate in the study. Each group gets one of the three types of muscle relaxer. The improvement in mobility of the 150 subjects is recorded and compared after 6 weeks of taking the drug.
experiment
Researchers are interested in studying the impact of journaling before taking an exam on exam performance. They have the students who show up 15 minutes early for a mathematics exam complete a journaling exercise before taking the exam. The students who completed the journaling exercise performed higher on the exam than the students who did not complete the journaling exercise. Based on these results, which of the following is the most appropriate conclusion in relation to cause and effect?
Bryan wants to know whether high school students prefer salty or sweet snacks. He creates a survey and collects preferences from everyone on her swim team. Which of the following best describes the population that the result of his survey can be extended to?
Bryan's teammates on the swim team
A high school is interested in seeing whether there are differences in extracurricular involvement among the different grades. They select the first 100 students who enter the school in the morning to survey.
Which of the following BEST describes how the selection process could impact the conclusion of the study?
Random selection was not used. The conclusion will not be representative of the larger population.
Suppose we have 4 different diets which we want to compare. The diets are labeled A, B, C, and D. We are interested in how the diets affect energy levels in mice. We have 20 mice available for the experiment, so we use 5 mice for each diet. describe a completely randomized design?
Label 20 cages from 1-20. In a bowl put 20 strips of paper labeled 1-20. In a second bowl put five labels each of A, B, C, and D. Catch a mouse and pick a number and letter from each bowl without replacement and assign the mouse.