Exam 1: What Is Statistics

The Attorney General of the state of California wanted to study criminal law in Los Angeles last year.He randomly selected 46,000 criminal records from the population of 1.5 million convicts in Los Angeles last year.From this sample, he calculated the proportion of litigations, the average amount of money involved per litigation, and the proportion of litigations resulting in a conviction.These calculations are all examples of doing ____________________ statistics.

A statistic is typically a known quantity while a parameter is typically an unknown quantity.

Briefly describe the difference between a population and a sample and give an example of each.

Identify each of the following as a use of descriptive statistics or inferential statistics. a. Finding the weights of a sample of 85 manufacturer parts. b. Calculating the average weight of 125 boxes shipped by FedEx. c. Estimating the percentage of the U.S.population that will vote for your favorite candidate in the next presidential election. d. Selecting a random sample of 190 babies born last year and using this information to estimate the birth weight of all babies born last year. e. Randomly selecting 225 cans of a brand of peas and using their average weight to decide whether the 15 oz.label on the cans is truthful or not.

At Cedar Rapids Community College, administrators want to determine the average commuting distance for their students who commute to school.They randomly select 250 students who commute and ask them the distance of their commute to campus.From this group a mean of 19.3 miles is computed. a. Describe/find the parameter. b. Describe/find the statistic. c. Describe the population. d. Describe the sample.

A descriptive measure that is computed from a sample is called a statistic.

You take a random sample to estimate a population mean and your results have a confidence level of 80%.That means the process you used will give you correct results 80% of the time.

In a sample of 350 students selected from a large college of business, 25% are found to be marketing majors.The 25% is a statistic.

What name do we give to a descriptive measure of a population?

A company has developed a new engine whose average lifetime is unknown.In order to estimate this average, 100 engines are randomly selected from a large production line and tested; their average lifetime is found to be 11 years.The 11 years represents a:

The Human Resources Director of a large hospital wants to determine the percentage of all employees who favor a newly proposed benefits package.He selects 300 employees at random and finds that 85% approve the newly proposed package.The percentage of all employees of this company who favor the newly proposed package is a(n) ____________________.

The Surgeon General wanted to study malpractice litigation in Chicago.A sample of 32,000 medical records was selected from all 3.5 million patients who were discharged during the year 2011.Using the information from the sample to make conclusions about malpractice litigation in Chicago is an example of doing ____________________ statistics.

A descriptive measure that is computed from a sample is called a:

A councilman who is running for the office of senator of a state with 3.5 million registered voters commissions a survey.In the survey, 46% of the 8,000 registered voters interviewed say they plan to vote for him.The population of interest is:

The Human Resources Director at Florida Atlantic University wishes to develop an employee benefits package.To get an idea of what components of a benefits package are most important, he selects 350 employees at random and asks them for their opinions.Numerically summarizing the preferences of these 350 employees is an example of doing ____________________ statistics.

A descriptive measure of a population is called a parameter.

The significance level measures the proportion of the time an inference about a population will be correct in the long run.

A study is under way to determine the average height of all 63,000 adult walnut trees in a certain national forest.The heights of 950 randomly selected adult walnut trees are measured and analyzed.The sample in this study is:

What name do we give to a descriptive measure of a sample?

The owner of a large manufacturing company wishes to develop a new employee health benefits package.He selects 500 employees at random and asks them about their preferences regarding their current health benefits package.The 500 employees selected is a(n) ____________________.