Exam 2: Flashcards
Which method will tend to give better statistical results?
- Observational studies
- Experiments
- Neither are likely to give good results.
- Observational studies and experiments are likely to give the same results.
Experiments
What do you call experimental units that are human beings?
- Populations
- Samples
- Subjects
- Experiments
Subjects
An experiment that favors a certain outcome over other outcomes is called ______.
biased
What is the best way to control for lurking variables?
- Compare two or more treatments.
- Randomize to assign experimental units to treatments.
- Repeat each treatment on many units.
- None of the above
Randomize to assign experimental units to treatments.
In order to determine whether smoking causes cancer, researchers surveyed a large sample of adults. For each adult, the researchers recorded whether the person had smoked regularly at any period in his or her life and whether the person had cancer. The researchers then compared the proportion of cancer cases in those who had smoked regularly at some time in their lives with the proportion of cases in those who had never smoked regularly at any point in their lives. The researchers found a higher proportion of cancer cases among those who had smoked regularly than among those who had never smoked regularly. What type of study is this?
An observational study that is a sample survey.
A market research company wishes to find out which of two Internet search engines the population of students at a university prefers to use: Google or Yahoo. A random sample of students is selected, and each one is asked to search for a certain subject using Google and then Yahoo, or vice versa. The order of the two searches was determined at random. They then indicated which Internet search engine they preferred. What type of study is this?
An experiment but not a double blind experiement.
Which of the following statements best describes the difference between an observational study and an experiment?
In an experiment, treatments are deliberately applied to individuals, and their responses are observed. In an observational study, individuals are observed, and variables of interest are measured, without any attempt to influence the responses.
In order to assess the opinion of students at a large university about campus snow removal, a reporter for the student newspaper interviews the first 12 students she meets who are willing to express their opinions. What type of sampling method was used to collect the data?
Voluntary response
Which of the following should a researcher be concerned about when conducting a sample survey?
- Having an accurate and complete list of the population under study
- Being unable to contact some of the units selected into the random sample
- Bias that arises because of the failure of respondents to answer questions honestly
- Questions phrased in such a way as to lead respondents to reply in a specific manner
A new drug has recently become available that, it is claimed, will relieve the symptoms of restless leg syndrome (RLS). A physician gave this drug to 30 patients who were known to suffer from RLS. Among these patients, 24 reported experiencing some significant relief, whereas six reported no change. What can be concluded from this information?
- This study has demonstrated the effectiveness of this new drug against the symptoms of RLS.
- Nothing can be concluded, because the number of patients in the sample is too small.
- Care must be taken in reaching any conclusion, because there is uncertainty due to the number of patients reporting no effect.
- Nothing can be concluded, because the experiment did not include a control group to compare the results against.
- Little can be concluded until the experiment is repeated with several more groups.
Nothing can be concluded, because the experiment did not include a control group to compare the results against.
The three basic principles of statistical design of experiments are:
Control, Randomization, and Repetition
Following the analysis of a well-designed, completely randomized experiment, it was reported that the observed effect was statistically significant. Which of the following statements best explains the meaning of the phrase “statistically significant”?
The observed effect was sufficiently large that it would rarely occur simply by chance.
In experimental design, explanatory variables are also called______.
factors
A television station is interested in predicting whether or not voters in its listening area are in favor of federal funding for abortions. It asks its viewers to phone in and indicate whether they are in favor of federal funding for abortions or are opposed to this. Of the 2241 viewers who phoned in, 1574 (70.24%) were opposed to federal funding for abortions. The number 70.24% is a _________.
statistic
