Exam 2: An Introduction to Statistics and Statistical Inference

The registrar at a small liberal arts college computes description summaries for all members of the entering class on a regular basis.For example, the average high school grade-point average (GPA) for the entering students in the most recent year was 3.16.The Chemistry department is interested in helping all new students who wish to take a chemistry class identify the appropriate course for them, so it offers a placement exam.The department randomly selects a subset of 175 students who took this exam during the past decade, and finds that they had an average score of 71.05 on the exam.The variable of interest to the Chemistry department in this study is:

A random sample of 10 cars is analyzed to evaluate the effect on horsepower of installing a computer chip modification.Based on the sample, researchers conclude that this modification will significantly increase a vehicle's horsepower if installed.This is an example of:

In a study that seeks to evaluate the effect that caffeine has on individuals with narcolepsy, 40 patients with this condition are randomly selected to participate in the study.Fifteen of the patients are given high doses of caffeine, 15 are given moderate doses, and 10 are given low doses over a period of 30 days.The variable of interest in this study is:

In the mid-1990s, a study was conducted to determine if arthroscopic surgery was an effective treatment for arthritis of the knee.Ten men were scheduled for surgery and each patient was anesthetized.But, after each patient was unconscious, the surgeon consulted a randomly generated code to determine whether to do the actual surgery, or to perform a "sham" surgery (make three small incisions in the knee, stitch the patient up, and leave a small scar).This is best described as a(n) _________________ study.

A sample of five people is analyzed to make a general statement about the population from which the people were sampled.This is an example of using:

All visitors to the CNN website are invited to take part in the daily poll.Is the resulting sample likely to be biased?

Which of the following is a reasonable estimate of the probability of lung cancer for a typical American adult?

In 2004, the San Francisco police began using DNA evidence in unsolved homicides.The crime lab found evidence that suggested John Puckett was a DNA match for a crime committed three decades earlier, based on 6 genetic locations.Usually, 13 genetic markers are required to distinguish between two different people.Jurors were told that the chance of randomly finding the defendant's DNA profile at the crime scene was 1 in 1.1 million.The jurors found the DNA evidence compelling and convicted Puckett of first-degree murder.This conclusion is an example of:

The effects of different lighting levels on productivity are evaluated using a designed experiment.Two hundred office workers who have the same basic job assignments are randomly selected to participate.Each worker is randomly assigned a different lighting level at his or her desk.Ambient (background) lighting is held constant for all workers.A benchmark of productivity is recorded for each worker.In this study, the sample is best described as:

The registrar at a small liberal arts college computes description summaries for all members of the entering class on a regular basis.For example, the average high school grade-point average (GPA) for the entering students in the most recent year was 3.16.The Chemistry department is interested in helping all new students who wish to take a chemistry class identify the appropriate course for them, so it offers a placement exam.The department randomly selects a subset of 175 students who took this exam during the past decade, and finds that they had an average score of 71.05 on the exam.The population of interest to the Chemistry department in this study is:

Nuclear power plants must discharge the excess heat generated in the nuclear process to the environment.Some plants exhaust this heat to nearby water sources.There is concern that this "thermal pollution" has an adverse effect on aquatic life near the plant.Researchers at the Environmental Protection Agency (EPA) catch 100 fish from the discharge pond of a particular power plant.They track the growth rates and life span of these fish, and compare these data to the data for fish from similar streams whose temperatures are not affected by the plant's thermal effluent.The sample in this experiment is:

A researcher wishes to obtain information about American males in the metro area who are between 20 and 25 years of age.He has a phone book that contains the land-line phone numbers of households in the metro area.The researcher uses a random number generator to select 50 households to call.Bearing in mind that he will be contacting only people who have a land line, is this a simple random sample?

In a(n) _______________, we investigate the effects of certain conditions on individuals or objects in the sample by manipulating the variable.