Chapter 1
When testing a new treatment, what is the difference between statistical significance and practical significance? Can a treatment have statistical significance, but not practical significance?
Statistical significance is achieved when the result is very unlikely to occur by chance. Practical significance is related to whether common sense suggests that the treatment makes enough of a difference to justify its use. It is possible for a treatment to have statistical significance, but not practical significance.
Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below. A researcher selects every 770 th social security number and surveys the corresponding person. nothing nothing nothing Which type of sampling did the researcher use?
Systematic sampling
State whether the data described below are discrete or continuous, and explain why. The numbers of countries in the world in different years
The data are Th discrete because the data can only take on specific values
Determine whether the given value is from a discrete or continuous data set. When a car is randomly selected, it is found to have 2 doors
A discrete data set because there are a finite number of possible values.
A researcher was once criticized for falsifying data. Among his data were figures obtained from 7 groups of rats, with 25 individual rats in each group. These values were given for the percentage of successes in each group: 53%, 58%, 63%, 46%, 48% ,68%,67% ,54%nothing nothing. What's wrong with those values?
All percentages of success should be multiples of 4. The given percentages cannot be correct.
Determine whether the value is from a discrete or continuous data set. Frequency of a guitar note is 430 Hz
Continuous
Determine whether the description corresponds to an observational study or an experiment. Eighty patients with stomach cancer are divided into two groups. One group receives an experimental drug to fight cancer comma the other a placebo. After one year comma the spread of the cancer is measured.
Experiment
In a survey of 615 human resource professionals, each was asked about the importance of the experience of a job applicant. The survey subjects were randomly selected by pollsters from a reputable market research firm.
It appears to be sound because the data are not biased in any way.
In a survey of 568 subjects, each was asked how often he or she played sports. The survey subjects were internet users who responded to a question that was posted on a news website
It is flawed because it is a voluntary response sample
Several studies showed that after regular exercise on a treadmill, subjects had lowered blood pressure. High blood pressure has been associated with increased risk of heart disease and stroke. A fitness equipment company financed this research. Identify what is wrong.
It is questionable that the sponsor is a It fitness equipment company because this sponsor can be greatly affected by the conclusion.
A study of an association between which ear is used for cell phone calls and whether the subject is left-handed or right-handed began with a survey e-mailed to 5000 people belonging to an otology online group, and 717 surveys were returned. (Otology relates to the ear and hearing.) What percentage of the 5000 surveys were returned? Does that response rate appear to be low? In general, what is a problem with a very low response rate?
Of the 5000 surveys, 14% were returned. This response rate appears to be low. It creates a serious potential for getting a biased sample that consists of those with a special interest in the topic.
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate. The rankings of songs in the top 100
Ordinal
Determine whether the given value is a statistic or a parameter. In a study of all 2477 students at a college comma it is found that 50 % own a computer.
Parameter because the value is a numerical measurement describing a characteristic of a population
Identify the type of sampling used (random, systematic, convenience, stratified, or cluster sampling) in the situation described below. In a poll conducted by a certain research center, 881 adults were called after their telephone numbers were randomly generated by a computer, and 26 % were able to correctly identify the vice president. Which type of sampling did the research center use?
Random sampling
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate. Monthly rainfall: 3.4 in comma 3.6 in comma 3.8 in comma 4 in comma and 4.2 in
Ratio
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate for the data below. Critic ratings of movies on a scale from 0 stars to 4 stars
The Th ordinal level of measurement is most appropriate because the data can be ordered comma but differences cannot be found or are meaningless
State whether the data described below are discrete or continuous, and explain why. The numbers of murders in different cities in a certain year
The data are discrete because the data can only take on specific values
Determine whether the data described below are qualitative or quantitative and explain why. The blood groups of Upper A comma Upper B comma AB comma and Upper O
The data are qualitative because they don't measure or count anything
Refer to the sample of body temperatures (degrees Fahrenheit) in the table below. Given these temperatures, what issue can be addressed by conducting a statistical analysis of the data? Subject 1 2 3 4 5 8 AM 97.0 98.5 97.6 97.7 98.7 12 AM 97.6 97.8 98.0 98.4 98.4
The data can be used to address the issue of whether there is a correlation between body temperatures at 8 AM and at 12 AM
Determine whether the given description corresponds to an observational study or an experiment. In a study of 403 students with a particular disease, the subjects were asked to complete a survey about their diet upon arrival to a hospital
The given description corresponds to Th an observational study
Determine whether the given value is a statistic or a parameter. A homeowner measured the voltage supplied to his home on 298 days of a given year, and the average (mean) value is 142.5 volts. Choose the correct answer below.
The given value is a statistic for the year because the data collected represent a sample
Determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate for the data below. Years in which a war was started
The interval level of measurement is most appropriate because the data can be ordered comma differences can be found and are meaningful comma and there is no natural starting zero point.
Determine if the following statement represents a meaningful ratio, so the ratio level of measurement applies. A movie with a 4-star rating is twice as good as one with a 2-star rating
The ratio level of measurement does not apply.
An article noted that chocolate is rich in flavonoids. The article reports that "regular consumption of foods rich in flavonoids may reduce the risk of coronary heart disease." The study received funding from a candy company and a chocolate manufacturers association. Identify and explain at least one source of bias in the study described. Then suggest how the bias might have been avoided.
The researchers may have been more inclined to provide favorable results because funding was provided by a party with a definite interest. The bias could have been avoided if the researchers were not paid by the candy company and the chocolate manufacturers
A particular country has 60 total states. If the areas of 20 states are added and the sum is divided by 20, the result is 186 comma 934 square kilometers. Determine whether this result is a statistic or a parameter
The result is a Th statistic because it describes some characteristic of a sample
A magazine ran a survey about a web site for downloading music. Readers could register their responses on the magazine's web site. Identify what is wrong.
The sample is a voluntary response sample, so there is a good chance that the results do not reflect the population.
A magazine, which does not accept free products or advertising from anyone, prints a review of new cars. Are there sources of bias in this situation?
There do not appear to be any sources of bias
Determine whether the source given below has the potential to create a bias in a statistical study. A certain medical organization tends to oppose the use of meat and dairy products in our diets, and that organization has received hundreds of thousands of dollars in funding from an animal rights foundation.
There does appear to be a potential to create a bias. There is an incentive to produce results that are in line with the organization's creed and that of its funders.
