Exam 7: Survey Sampling and Inference

A polling agency wants to compare support for the president's foreign policies between men and women. They surveyed 2500 U.S. citizens and found a 95% confidence interval for the difference in proportions between men and women who support the president's foreign policies as (-0.05 to -0.025) where population 1 is men and population 2 is women. Select the correct interpretation of this result.

A random sample of 950 adult television viewers showed that 48% planned to watch sporting event X. The margin of error is 4 percentage points with a 95% confidence level. Does the confidence interval support the claim that the majority of adult television viewers plan to watch sporting event X?

A group of screwdrivers produced in a day at a particular factory has a defect rate of 0.7%. Suppose a quality inspector randomly inspects 500 screwdrivers. Complete the following statement: The quality inspector should expect ____defective screwdrivers, with an error of ____.

Suppose that the age of all the U. S. vice presidents when they took office was recorded. The collection of the ages of all the U. S. vice presidents when they took office is a .

Suppose that you and a friend read the following statement in a news report, "A recent poll found that 54% of voters, give or take 3%, plan to vote for candidate X in the next election (with a confidence level of 95%)". Your friend then makes the statement, "Hey, look, there's a 95% chance that somewhere between 51% and 57% of voters plan to vote for candidate X!" How would you explain to your friend why his statement is incorrect, be sure to provide your friend with the correct interpretation of the confidence interval.

Complete the statement by filling in the blanks. When constructing a confidence interval, if the level of confidence increases, the margin of error must _____ and the confidence interval will be .

Use the following information to answer questions (14)-(15). In a recent poll of 1100 randomly selected home delivery truck drivers, 26% said they had encountered an aggressive dog on the job at least once. -What is the margin of error, using a 95% confidence level, for estimating the true population proportion of home delivery truck drivers who have encountered an aggressive dog on the job at least once? (Round to the nearest thousandth)

Describe the importance of how survey questions are phrased - in particular, the effect on the sample results. Explain how such a sample may not be reflective of the population.

Is it plausible that more than 10% of Americans believe in aliens? A random sample of 2000 adult Americans were surveyed and 15% of them said that they believed in aliens. Find the 95% confidence interval for the proportion of Americans who believe in aliens then choose the correct interpretation. (Round to the nearest tenth of a percent)

Use the following information to answer questions (6)-(8). A marble manufacturer advertises that its bags of marbles will contain 25% "milky-white" marbles. Suppose that a bag containing 80 marbles is inspected. -What is the standard error? Round to the nearest tenth of a percent.

A sampling method should be as precise and accurate as possible. Explain what these two terms mean and how each is measured.

Use the following information to answer questions (15)-(16). In a recent poll of 900 randomly selected adults, 37% reported that they could not swim 24 yards (the length of a typical gymnasium lap pool). -What is the margin of error, using a 95% confidence level, for estimating the true proportion of adults who self-report that they cannot swim 24 yards? Round to the nearest thousandth.

Use the following information to answer questions (6)-(8). A marble manufacturer advertises that its bags of marbles will contain 25% "milky-white" marbles. Suppose that a bag containing 80 marbles is inspected. -What value should we expect for our sampling percentage of milky-white marbles? How many marbles would this be? Round to the nearest whole marble.

Researchers are interested in learning more about the age of young adults who watch a certain television program. By interviewing people at a shopping mall, they can identify people who watch this show. The collection of the ages of these young adults who watch this television program is a _____________.

All daily maximum temperatures in August last year for all major U.S. cities were recorded. The mean of all maximum temperatures would be a _____________.

According to the manufacturer of the candy Skittles, 20% of the candy produced are red. If we take a random sample of 100 bags of Skittles, what is the probability that the proportion in our sample of red candies will be less than 20%? Which statement, if any, is not true for the conditions to use the Central Limit Theorem?

Complete the statement by filling in the blank. When constructing a confidence interval, a larger sample size will _________ the margin of error and the confidence interval will be