Exam 2: An Introduction to Statistics

An experiment that simply records the direction a rat turns at a particular junction in a maze is a(n)_____ study.

To evaluate the objectivity of a certain professor's grading,20 classes that she previously taught are randomly selected for auditing.The proportion of male students that pass in each class is compared to the proportion of female students for each selected class.The sample in this study is:

In a(n)_____,we merely observe the response for a specific variable for each individual or object.

The 2009 National Survey on Drug Use and Health selected a random sample of U.S.college students and asked them about illicit drug use.Roughly 23% of the students surveyed reported using illicit drugs in the past year.The variable in this study is:

Ten apples are taken off the top of a truckload of apples,and the amount of bruising on those apples is measured in order to estimate how much bruising there is,on average,in the whole truckload.Is this a simple random sample?

The time required to cure concrete is pivotal in the construction business.Insufficient curing time results in lower structural strength,which can create hazardous design conditions.Too much time wastes valuable resources and may result in greatly inflated building costs.To help ascertain the optimum curing time,a random sample of 80 poured concrete foundations is drawn.The total time to completely cure each foundation is recorded.This study is BEST described as a(n)_____ study.

If all visitors to the CNN Web site are invited to take part in the daily poll online,is the resulting sample likely to be biased?

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 GPA for the entering students in the most recent year was 3.16.The Chemistry department is interested in helping all students who wish to take a chemistry class identify the appropriate course,so they offer a placement exam.They randomly select a subset of 175 students who took this exam during the past decade,and found they had an average score on the exam of 71.05.The variable of interest to the Chemistry department in this study is the:

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 5¹/₂ genetic locations.Usually 13 genetic markers are used 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:

In many real-world settings,it is not possible or feasible to know the characteristics of the population.Since we cannot safely assume these characteristics,we must use the information from a sample to answer questions concerning the population.In cases such as these,we are dealing with a(n)_____ problem.

A psychologist wishes to test a behavioral modification therapy that is claimed to improve the behavior of pre-teen autistic children.She randomly selects 20 pre-teen autistic children and exposes half of the group to the behavioral modification therapy while the other half continue with their standard treatment regimen.A standardized behavioral test is administered to each child both before and after his/her respective treatment.The population in this experiment is:

In a study that seeks to evaluate the effect caffeine has on narcoleptics,40 narcoleptic patients are randomly selected to participate.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 total amount of time they slept over the 30 days was recorded.This is BEST described as a(n)_____ study.

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