A survey found that 28 of 79 people who don’t drink coffee often have trouble sleeping and 26 of 81 coffee drinkers often have trouble sleeping.  Construct and interpret a 95% confidence interval of the difference between the proportion of non-coffee drinkers who have trouble sleeping and the proportion of coffee drinkers who have trouble of sleeping.

A quality control engineer would like to estimate the mean fill amount of a certain bottle-filling machine to within 0.05 liter.  If we assume that the population standard deviation is 0.17 liters, how large of a sample is needed to estimate m with 95% confidence?

The table below represents class and voting data for 100 students who filed out the questionnaire. If a student is selected at random (from these 100 students), a) find the probability that the student is a freshman. b) find the probability that the student is a freshman or voted in the elections.

Identify which type of sampling is described. A market researcher selects 500 drivers under 30 years of age and 500 drivers over 30 years of age.

There are eight multiple-choice questions on an exam, each question having five choices (A, B, C, D, or E).  Suppose the student guesses on each question (Note: there is only one correct answer per question). a) Find the probability that the student get exactly 3 correct answers. b) Find the probability that the student get at least one correct answer. c) Find the mean and standard deviation of correct answers obtained by a student

The owner of a computer repair shop has determined that their daily revenue has mean $7500 and standard deviation $1400.  The daily revenue totals for the next 30 days will be monitored.  What is the probability that the mean daily revenue for the next 30 days will exceed $8000?

In recent years, there has been increasing concern about health effects of computer terminals.  It is know that the miscarriage rate under general conditions is about 15%.  A random sample of 700 pregnant women working with a computer 1 to 20 hours per week was taken.  For this sample, there were 125 miscarriages. a) We wish to test the hypothesis that “short-term exposure (e.g., 1 to 20 hours per week) to computer terminals increases the rate of miscarriages”.  State the appropriate hypotheses. b) Using a significance level of 0.05, test the hypotheses in part (a).

A company that sells annuities must base the annual payout on the distribution of the length of life of the participants in the plan.  Suppose the distribution of the lifetimes of male participants is approximately normal with a mean of 69 years and a standard deviation of 3.8 years. a) What is the probability that a male participant would die before reaching the standard retirement age of 65? b) At what age have the payments ceased for approximately 95% of the male plan participants?

Which of the following best exemplifies the U.S.’s “checks and balances” system in practice?

What was the Supreme Court’s majority ruling in Schenck v. United States? What is its relevance for thinking about the relationship between civil liberties and wartime?