FiltersDone

Question type

Essay

Multiple Choice

Short Answer

True False

Matching

Exam 18: Confidence Intervals for Proportions

Show Answer

Share

---

All types

Filters

Study FlashcardsPractice ExamLearn

Question 21

Multiple Choice

Review LaterAdd Note

Review Later

Data collected by child development scientists produced the following 90% confidence interval for the average age (in months) at which children say their first word: 10.2 < μ(age) < 13.5.

A) 90% of the children in this sample said their first word when they were between 10.2 and 13.5 months old.
B) We are 90% sure that the average age at which children in this sample said their first word was between 10.2 and 13.5 months.
C) Based on this sample,we can say,with 90% confidence,that the mean age at which children say their first word is between 10.2 and 13.5 months.
D) We are 90% sure that a child will say his first word when he is between 10.2 and 13.5 months old.
E) If we took many random samples of children,about 90% of them would produce this confidence interval.

Correct Answer

verified

Show Answer

Question 22

Multiple Choice

Review LaterAdd Note

Review Later

Of 314 randomly selected medical students,25 said that they planned to work in a rural community.Construct a 95% confidence interval for the percentage of all medical students who plan to work in a rural community.

A) (4.40%,11.5%)
B) (4.97%,11.0%)
C) (5.45%,10.5%)
D) (4.03%,11.9%)
E) (7.02%,8.90%)

Correct Answer

verified

Show Answer

Question 23

Multiple Choice

Review LaterAdd Note

In a survey of 1,000 television viewers,40% said they watch network news programs.For a 99% confidence level,the margin of error for this estimate is 3.99%.If we only want to be 90% confident,how will the margin of error change?

A laboratory tested 60 chicken eggs and found that the mean amount of cholesterol was 241 milligrams with s = 14.7 milligrams.Construct a 95% confidence interval for the true mean cholesterol content of all such eggs.

How tall is the average student on your campus? To determine this,you measure the height of a random sample of 200 students,finding a mean height of 166.60 cm and a standard deviation of 5.64 cm.Construct a 90% confidence interval for the mean height of your fellow students.

A recent poll of 500 residents in a large town found that only 36% were in favor of a proposed referendum to build a new high school.Find the margin of error for this poll if we want 90% confidence in our estimate of the percent of residents in favor of this proposed referendum.

Of 125 adults selected randomly from one town,28 of them smoke.Construct a 99% confidence interval for the percentage of all adults in the town who smoke.

A researcher wants to estimate the mean cholesterol level of people in his city.A random sample of 221 people yields an average cholesterol level of 219,with a margin of error of ±12.Assume the researcher used a confidence level of 90%.

An advertising firm wants to confirm estimates that 18% of households will buy something on the internet next year.What sample size will produce a margin of error of 7% with 90% confidence level?

A random sample of 64 statistics students at a small college were given a surprise quiz out of 40 marks.The average score was 27 with a standard deviation of 5.Find a 95% confidence interval for the mean quiz score for all statistics students at this college.

In a survey of 1,000 television viewers,40% said they watch network news programs.For a 90% confidence level,the margin of error for this estimate is 2.5%.If we want to be 99% confident,how will the margin of error change?

How much fat do reduced fat cookies typically have? You take a random sample of 120 reduced-fat cookies and test them in a lab,finding a mean fat content of 3.2 grams and a standard deviation of 1.9 grams of fat.Create a 99% confidence interval for the mean grams of fat.

A survey found that 79% of a random sample of 1024 Canadian adults approved of cloning endangered animals.Find the margin of error for this survey if we want 90% confidence in our estimate of the percent of Canadian adults who approve of cloning endangered animals.

A survey of shoppers is planned to see what percentage use credit cards.Prior surveys suggest 56% of shoppers use credit cards.How many randomly selected shoppers must we survey in order to estimate the proportion of shoppers who use credit cards to within 1% with 95% confidence?

Analysis of a random sample of 250 Nova Scotia nurses produced a 95% confidence interval for the mean annual salary of $42,841 < μ(Nurse Salary) < $49,696.

A random sample of clients at a weight loss centre were given a dietary supplement to see if it would promote weight loss.The centre reported that the 100 clients lost an average of 47 pounds,and that a 95% confidence interval for the mean weight loss this supplement produced has a margin of error of ±9 pounds.

A sociologist develops a test to measure attitudes about public transportation,and 100 randomly selected subjects are given the test.Their mean score is 76.2 and their standard deviation is 21.4.Construct the 95% confidence interval for the mean score of all such subjects.

How many unpopped kernels are left when you pop a bag of microwave popcorn? Quality control personnel at Yummy Popcorn take a random sample of 80 bags of popcorn.They pop each bag in a microwave and then count the number of unpopped kernels.The following interval is produced: T-interval for μ : with 99% Confidence, 11 < μ(unpopped) < 25

A credit union took a random sample of 400 accounts and obtained the following 90% confidence interval for the mean checking account balance at the institution: $2,185 < μ(balance) < $3,846.

A researcher wishes to estimate the proportion of fish in a certain lake that is inedible due to pollution of the lake.How large a sample should be tested in order to be 99% confident that the true proportion of inedible fish is estimated to within 6%?