Estimate a population mean with a confidence interval

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Reference no: EM132572964

Homework - Confidence Intervals

Question #1
If n=18, x‾ (x-bar)-44, and s=11, construct a confidence interval at a 99% confidence level. Assume the data came from a normally distributed population.

Give your answers to one decimal place.

Question #2
You intend to estimate a population mean with a confidence interval. You believe the population to have a normal distribution. Your sample size is 14.

Find the critical value that corresponds to a confidence level of 98%.
(Report answer accurate to three decimal places with appropriate rounding.)
ta/2='

Question #3
You are a researcher studying the lifespan of a certain species of bacteria. A preliminary sample of 25 bacteria reveals a sample mean of x‾= 72 hours with a standard deviation of 8 = 4.8 hours. You would like to estimate the mean lifespan for this species of bacteria to within a margin of error of 0.75 hours at a 98% level of confidence.

What sample size should you gather to achieve a 0.75 hour margin of error? Round your answer up to the nearest whole number.
n = bacteria

Question #4
Out of 400 people sampled, 268 had kids. Based on this, construct a 90% confidence interval for the true population proportion of people with kids.
Give your answers as decimals, to three places

Question #5
A political candidate has asked you to conduct a poll to determine what percentage of people support her.
If the candidate only wants a 9% margin of error at a 90% confidence level, what size of sample is needed?
Give your answer in whole people.

Question #6
A student was asked to find a 98% confidence interval for the proportion of students who take notes using data from a random sample of size n = 90. Which of the following is a correct interpretation of the interval 0.15 < p < 0.27?
Check all that are correct,

With 98% confidence, the proportion of all students who take notes is between 0.15 and 0.27.
With 98% confidence, a randomly selected student takes notes in a proportion of their classes that is between 0.15 and 0.27.
There is a 98% chance that the proportion of the population is between 0.15 and 0.27. 0 The proprtion of all students who take notes is between 0.15 and 0.27, 98% of the time.
There is a 98% chance that the proportion of notetakers in a sample of 90 students will be between 0.15 and 0.27.

Question #7
If n-520 and /3 (p-hat) = 0.49, construct a 90% confidence interval.
Give your answers to three decimals.
<p<

Question #8
Insurance companies are interested in knowing the population percent of drivers who always buckle up before riding in a car. They randomly survey 414 drivers and find that 281 claim to always buckle up. Construct a 95% confidence interval for the population proportion that claim to always buckle up.

Question #9
If n=350 and p' (p-prime) = 0.29, construct a 99% confidence interval.
Give your answers to three decimals.
<p<
The video uses /3 (p-hat) in place of p'.

Question #10
Insurance companies are interested in knowing the population percent of drivers who always buckle up before riding in a car. They randomly survey 408 drivers and find that 315 claim to always buckle up. Construct a 81% confidence interval for the population proportion that claim to always buckle up. Use interval notation, for example, [1,5]

Reference no: EM132572964

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