MATH 121 (PRACTICE QUIZ 1)
In 2008, a highway safety administration reported that the number of pedestrian fatalities in City A was 65 and that the number in City B was 45. Can we conclude that pedestrians are safer in City B? Why or why not?
No, in order to compare the fatalities the statistics must include the number of fatalities per pedestrian. There may be fewer pedestrians in City B causing the difference.
The accompanying data were collected from a statistics class. The column heads give the variable, and each of the rows represents a student in the class. Suppose you decided to code handedness using Right-handed as the label for the column. How many ones and how many zeros would there be?
Remember count the right handed and left
Two sections of statistics are offered, the first at 8 a.m. and the second at 10 a.m. The 8 a.m. section has 25 women, and the 10 a.m. section has 15 women. A student claims this is evidence that women prefer earlier statistics classes than men do. What information is missing that might contradict this claim?
The percentage of female students in the two classes is unknown. There may be more females in the 8 a.m. because there are more students in the 8 a.m. class than the 10 a.m. class. This claim could be true only if the classes were the same size.
A study concludes that the use of pesticides is associated with the development of Parkinson's disease, a neurological disease that causes people to shake. The study reported that exposure to bug killers and weed killers is "associated with" an increase of 33% to 80% in the chances of getting Parkinson's. Does this study show that pesticides cause Parkinson's disease? Why or why not?
The study does not show that pesticides cause Parkinson's disease. This was an observational study because researchers could not have deliberately exposed people to pesticides. Observational studies cannot conclude causation.
Indicate whether the following study is an observational study or a controlled experiment. Patients with Alzheimer's disease are randomly divided into two groups. One group is given a new drug, and the other is given a placebo. After six months they are given a memory test to see whether the new drug fights Alzheimer's better than a placebo.
This is a controlled experiment. The researchers randomly assigned patients to either a treatment or control group, and they gave the patients a test afterwards to identify the effect of the new drug. This satisfies a key criterion of controlled experiments.
Indicate whether the following study is an observational study or a controlled experiment. Records of patients who have had broken ankles are examined to see whether those who had physical therapy achieved more ankle mobility than those who did not.
This is an observational study. Since the researchers did not randomly assign subjects to the control or treatment group beforehand, they did not satisfy a key feature of controlled experiments.
A doctor who believes strongly that antidepressants work better than "talk therapy" tests depressed patients by treating half of them with antidepressants and the other half with talk therapy. After six months the patients are evaluated on a scale of 1 to 5, with 5 indicating the greatest improvement. Answer parts (a) through (d) below.
a. If the doctor decides on the treatment, this could introduce bias. b.The doctor should randomly assign the patients to the different treatments. c. If the doctor is aware of the treatment each patient receives, that might influence his opinion about the effectiveness of the treatment. d. To prevent bias, the experiment should be double-blind. Neither the patients nor the doctor evaluating the patients should know whether each patient received medication.
A group of overweight people are asked to participate in a weight loss program. Participants are allowed to choose whether they want to go on a vegetarian diet or follow a traditional low-calorie diet that includes some meat. Half of the people choose the vegetarian diet, and half choose to be in the control group and continue to eat meat. Suppose that there is greater weight loss in the vegetarian group. Complete parts (a) and (b) below.
a. People who are not prepared to change their diet very much (such as by excluding meat) might also not change other factors that affect weight, such as how much exercise they get. b. The experiment would be improved if some subjects were randomly assigned to eat meat and the remaining subjects to consume a vegetarian diet.
a.a. A statistics class is made up of 1919 men and 2222 women. What percentage of the class is male? b.b. A different class has 279279 students, and 48.748.7% of them are men. How many men are in the class? c.c. A different class is made up of 4040% women and has 2020 women in it. What is the total number of students in the class?
a. The statistics class is 46.346.3% male. (Round to one decimal place as needed.) b. There are 136136 males in the class. (Round to the nearest whole number as needed.) c. The class consists of 5050 students. (Round to the nearest whole number as needed.)
A doctor reported on a study that treated children who had sleep apnea, which interferes with breathing while a child is asleep. In the study, 464 children, 5 to 9 years of age, were randomly assigned to either surgery or to be under constant watch for a certain period of time. The study found that there were significantly greater improvements in behavioral, quality-of-life, and sleep study findings in the group that had surgery than the group assigned to constant watch. Complete parts (a) and (b) below.
a. The study was a controlled experiment because the children were randomly assigned to either surgery or constant watch. This is essential to conducting a controlled experiment. b. We can conclude that the early surgery caused the improvements because it was a randomized controlled experiment.
Write these data as they might appear in stacked format with codes. 1. 0
b. Write these data as they might appear in unstacked format. sweet and salty only
