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WorksheetsConfidence Intervals - Practice quiz.
Total questions: 15
Worksheet time: 24mins
A sample of 20 cupcakes found the interval for average calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?
We are 95% confident that the true mean caloric content can be found with a sample of 150 to 350 cupcakes.
We are 95% confident that the interval (150, 350) captures the true average caloric content.
We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.
None of these are correct.
Complete the equation to calculate a confidence interval:
point estimate +/- _____
standard deviation
margin of error
critical value
confidence level
Given the Critical Value of Z = 2.11 (the Z- score that corresponds to particular confidence interval), find the Confidence Level.
96.52%
0.9652
.9826
98.26%
A person selects a random sample of 15 credit cards and determines the annual interest rate, in percent, of each one. The sample mean is 12.42 with a sample standard deviation of 1.3. It is desired to construct a 90% Confidence Interval.
Find the Standard Error to three decimal places.
0.336
0.33566
13.156
0.087
The weights of packets of chips are known to be distributed with a variance of 2.56 grams.A sample of 100 packs were tested and the mean weight was 24.1 grams.
Calculate a 99% confidence interval for the population mean 𝜇.
23.78 ≤ 𝜇 ≤ 24.41
23.78 ≤ 𝜇 ≤ 24.51
23.69 ≤ 𝜇 ≤ 24.51
23.83 ≤ 𝜇 ≤ 24.51
23.83 ≤ 𝜇 ≤ 24.36
A random sample of size 25 is taken from a normal population with a standard deviation of 2.5.
The mean of the sample was 17.8.
Find a 99% confidence interval for the population mean μ .
(16.51, 19.09)
(17.54, 18.05)
(16.03, 19.49)
(19.09, 16.51)
A random sample of size 25 is taken from a normal population with a standard deviation of 2.5.
The mean of the sample was 17.8.
What size sample is required to obtain a 99% C.l. of the width of 1.5?
Round your answer to the nearest whole number.
(a)
A normal distribution has a standard deviation of 15. Estimate the sample size required if a 90% confidence interval for the mean should be in a width of 2.
(a)
A normal distribution has a standard deviation of 15. Estimate the sample size required if a 95% confidence interval for the mean should be in a width of 2.
(a)
A normal distribution has a standard deviation of 15. Estimate the sample size required if a 99% confidence interval for the mean should be in a width of 2.
(a)
We measure the height of 40 randomly selected women, in which the mean height is 175cm. We also know the standard deviation is 20cm. Which of the following represents a 95% Confidence Interval?
135cm ± 20cm
175cm ± 6.2cm
155cm ± 6.2cm
175cm ± 35cm
A sample of 20 cupcakes found the interval for average calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?
We are 95% confident that the true mean caloric content can be found with a sample of 150 to 350 cupcakes.
We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.
We are 95% confident that the interval (150, 350) captures the true average caloric content.
None of the above.
A population has a standard deviation of σ = 17.3. How large of a sample must be drawn so that a 95% confidence interval for µ will have a Margin of Error equal to 1.4?
586.6
587
586
585
What z-score would you use if you were looking to construct a confidence interval with a 99% level of confidence? write your answer to 2 decimal places.
(a)
