EBook Problems GLM Predict

EBook Problems Set - Variation and Prediction Intervals

Problem 1

Two researchers are going to take a sample of data from the same population of physics students. Researcher A will select a random sample of students from among all students taking physics. Researcher B's sample will consist only of the students in her class. Both researchers will construct a 95% confidence interval for the mean score on the physics final exam using their own sample data. Which researcher's method has a 95% chance of capturing the true mean of the population of all students taking physics?

• Choose one answer.

(a) Research B

(b) Researcher A

(c) Both methods have a 95% chance of capturing the true mean

(d) Neither

Answer

 (b)

Problem 2

A random sample of 150 UCLA students found that 35% of the respondants wanted a elevator to replace Bruin Walk. A 95% confidence interval for the percentage of all UCLA students who feel this way is approximately:

• Choose one answer.

(a) (24%, 46%)

(b) (32%, 38%)

(c) The sample size is too small to compute a confidence interval.

(d) (27%, 43%)

Answer

 (d)

Problem 3

According to Terry Prachett, the short unit of time in the multiverse is the New York second, defined as the time interval between the light turning green and the cab behind you honking. A magazine took a poll of 100 New Yorkers and found that 90 people agree with that statement wholeheartedly. Which of the following is a 90% confidence interval for the proportion of people who agree with that statement?

• Choose one answer.

(a) 0.9 +\- 0.50

(b) 0.9 +\- .05

(c) 0.9 +\- .03

(d) 0.9 +\- .06

Answer

 (b)

Problem 4

A national poll found that 62% of all Americans agreed that more attention should be paid to mental health of war veterans. If a simple random sample of 326 people was used to make a 95% confidence interval of (0.57,0.67), what is the margin of error?

• Choose one answer.

(a) 0.03

(b) 0.05

(c) 0.12

(d) In order to calculate the margin of error, we need the p-value of the population.

Answer

 (b)

Problem 5

Hermione Granger is on a mission this year to complain about the astronomical cost of wizarding books to the Hogwart board of administrators. Given that the population mean for book cost is 10 and a standard deviation of 2 galleons, If Hermione were to take a simple random sample of 49 students and make a 68% confidence interval, what would be the range of values for the sample mean or Xbar?

• Choose one answer.

(a) 8 and 12 galleons

(b) 9.4 and 10.6 galleons

(c) 6 and 14 Galleons

(d) 9.7 and 10.3 galleons

Answer

 (d)

Problem 6

A 95% confidence interval indicates that:

• Choose one answer:

(a) 95% of the intervals constructed using this process based on samples from this population will include the population mean

(b) 95% of the time the interval will include the sample mean

(c) 95% of the possible population means will be included by the interval

(d) 95% of the possible sample means will be included by the interval

Answer

 (a)

Problem 7

Suppose we want to find out if a coin is not fair. To test this hypothesis we flip the coin 100 times, and in 63 out of 100 flips we get heads. We construct the confidence interval and find it to be (.53,.73). Interpret this confidence interval.

• Choose one answer.

(a) 95 is the Z score that corresponds to our distribution of sample means

(b) Confidence is something you learn at fraternity parties

(c) 95% of the time the true proportion of flips that are heads is between .53 and .73

(d) If we were to repeat this experiment over and over again, 95 times out of 100 our Confidence interval would cover the true proportion of flips that are heads

Answer

 (d)

Problem 8

A 95% confidence interval is calculated for a sample of weights of 100 randomly selected pigs, and is (42 pounds, 48 pounds). Will the sample mean weight fall within the confidence interval?

• Choose one answer.

(a) Yes

(b) We need more information to determine if this is true.

(c) No

Answer

 (a)

Problem 9

The average number of fruit candies in a large bag is estimated. The 95% confidence interval is (40, 48). Based on this information, you know that the best estimate of the population mean is:

• Choose one answer.

(a) 43

(b) 40

(c) 45

(d) none of the above.

(e) 44

Answer

 (e)

Problem 10

Suppose we plan to take a random sample of adults in the U.S. and determine the percent of them who have attended church in the last 30 days. We calculate a 90% confidence interval for the proportion of all adults in the U.S. who attended church in the last 30 days. Which of the following changes in our plans would result in a wider confidence interval?

• Check all that apply.

(a) Using an 85% confidence level.

(b) Using a 95% confidence level.

(c) Using a larger sample.

(d) Using a smaller sample.

Answer

 (b) , (d)

Problem 11

Kevin has always, ever since he was a wee lad, wondered what proportion of the candies in M&M chocolate candies bags are yellow. However, his persistent calls to the M&M headquarter were of no avail. Now that he wields the awesome power of being a TA for Stat 10, he makes each of his 200 students go buy a M&M bag, count the colors, and compute a 99% confidence intervals for the yellow candy proportion. Assume that each M&M bag is a random sample, approximately how many of the 200 confidence intervals will not capture the true population proportion for yellow M&M's?

• Choose one answer.

(a) Not enough information for an answer

(b) 0 to 4

(c) 4 to 8

(d) 12 to 14

(e) 8 to 12

Answer

 (b)

Problem 12

A 95% confidence interval for the proportion of U.S. adults who favor the death penalty is given by (0.03, 0.09). Is the following statement true or false?

"There is a 95% probability that an adult in the US is in favor of the death penalty."

(a) True

(b) False

Answer

 (b)

Problem 13

Suppose that one day, after a refreshing work out at the gym, you want to know how many of the people in the North campus know who John Wooden is. You walk into the deep North, carefully avoiding the people holding skulls and muttering in Elizabethan english. Once you are at the center of North campus, you nicely ask the North campus majors to stop chasing butterflies and then took a random sample of 100 students. 30 say that they know who John Wooden is.

What is the 95% confidence interval for the true percentage of North campus majors who know about John Wooden?

• Choose one answer.

(a) 29.5 to 30.5%

(b) 29.95 to 30.05%

(c) 20.8 to 39.2%

(d) 25.4 to 34.9%

Answer

 (c)

Problem 14

The church of Pastafarian wants to know how many people in a city of 1 million would like to attend its church services. After sending out volunteers to do a simple random sample, the church finds a 90% confidence interval. Which of the following should have been done to make the confidence interval smaller?

• Choose one answer.

(a) Not enough information to tell

(b) Increasing the sample size

(c) Decreasing the sample size

(d) Use a 68% confidence interval instead

Answer

 (a)

Problem 15

A few years after the events of 'The Jedi Returns', Luke Skywalker, as the new Jedi Master, is thinking of establishing a Jedi church on his home world of Tatooine. He would like to know what proportion of people would be interested in coming to church, so he uses his Jedi Mind powers to select a simple random sample of 1000 people, and then read their minds to see whether they would are interested in a Jedi church.

He computes a 95% confidence interval. What could he have done in order to increase the decrease the length of the confidence interval? Check all that applies

• Choose at least one answer.

(a) Decrease the sample size

(b) Increase the sample size

(c) Use a 68% confidence interval instead

(d) Use a 99% confidence interval instead

Answer

 (b) , (c)

Problem 16

A college instructor wants to be 99% certain of the mean math anxiety score for freshman enrolled in college algebra. What is the best way for him to do this?

• Choose one answer.

(a) Test on mean against a hypothesized constant.

(b) Test the difference between the two means of independent samples.

(c) Use a chi-squared test of association.

(d) test for a difference in more than two means (one way ANOVA).

(e) Test the difference in means between two paired or dependent samples.

(f) Test that a correlation coefficient is not equal to 0 (correlation analysis).

(g) Construct a 99% confidence interval.

Answer

 (g)

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