Ch.3 What do Samples Tell Us?

A simple random sample of 64 people finds that 38 of the 64 like the television show "American Idol." The margin of error for 95% confidence is approximately 1/n‾√. The margin of error is _____. (Enter your answer to three decimal places.)

.125 1. 1/√64 2. 1/8 3. .125

A simple random sample of 64 people finds that 38 of the 64 like the television show "American Idol." The proportion of people in the sample who like "American Idol" is computed as _____.

.59375 1. 38/64 2. .59375

Which sample size would have the lowest variability? (increasing the sample size, decreases variability)

80

A news report states that 80% of Americans own a smartphone with a margin of error of 3%. This means that the confidence interval is between 77% and _____% of Americans who own a smartphone.

83% * minus 3%= 77% * plus 3%= 83%

Which of the following statements explains why margin of error is reduced when the sample size is larger?

There will be less variability from sample to sample when we have larger samples.

A polling company states that 90% of Americans own a handheld music storage device with a margin of error of 3%. If the confidence level is 95%, we are 95% _____ that between 87% and 93% of all Americans own a handheld music playing device.

confident

If we want to cut the margin of error in half, we must use a sample ________ times as large.

four

To decrease the margin of error, you must _____ the sample size.

increase

The population proportion ____ is usually _____.

p; unknown

A researcher takes a simple random sample of 100 individuals to determine what percentage of the American public prefers Pepsi to Coke. The _____ is the proportion of the American public who prefer Pepsi to Coke.

parameter

The variability of a statistic from a random sample depends on the size of the _____.

sample

If we have a population of sufficient size, which of the following will affect variability more?

sample size

In the formula used to compute the margin of error for 95% confidence, 1/n‾√, what does n represent?

sample size

A(n) _____ is a number that describes the sample.

statistic

We often use a known _____ to estimate an unknown parameter.

statistic

News stories reporting poll results often include the statement "results for subgroups have a larger margin of error." This is because _____.

subgroups have a smaller sample size.