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- 1. Multiple Choice
A random 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.
Based on the sample, we are 95% confident that true average caloric content is in the interval 150 to 350 calories
We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.
None of these are correct.
- 2. Multiple Choice
A quality control specialist at a glass factory must estimate the mean clarity rating for a new batch of glass using a sample of 18 glass sheets from the batch. Past investigations show that clarity ratings are normally distributed. The specialist decides to use a t-distribution rather than a z-distribution because ...
The t distribution is more accurate than a z distribution.
Clarity ratings for the entire bacth are normally distributed.
The t-distribution will create a narrower interval than z.
The standard deviation for the population is unknown.
- 3. Multiple Choice
Thirty randomly selected students took the calculus final. If the sample mean was 92 and the standard deviation was 9.4, construct a 99 percent confidence interval for the mean score of all students from which the sample was gathered.
89.08 < μ < 94.92
87.27 < μ < 96.73
87.29 < μ < 96.71
87.77 < μ < 96.23
- 4. Multiple ChoiceWhich of the following changes to a study would result in a narrower confidence interval?increasing the confidence level, increasing the sample sizedecreasing the confidence level, decreasing the sample sizeincreasing the confidence level, decreasing the sample sizedecreasing the confidence level, increasing the sample size.
- 5. Multiple Choice
The lifetime of a certain type of battery is known to be normally distributed with a standard deviation of 20 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 99% confidence interval for the mean lifetime of this type of battery.
What is the Confidence Interval to one decimal place?
(114.5, 125.6)
(112.8, 127.4)
(112.82, 127.38)
(114.56, 125.64)
- 6. Multiple Choice
The football coach randomly selected ten players and timed how long each player took to perform a certain drill. The times (in minutes) were: 13.2, 5.1, 7.5, 8.0, 12.7, 7.6, 13.8, 14.5, 7.7, and 10.5. Determine a 95 percent confidence interval for the mean time for all players.
(2.30, 7.82)
(7.82, 12.30)
(7.72, 12.40)
(2.40, 7.72)
- 7. Multiple Choice
Which of the following does NOT have an affect on the margin of error of a confidence interval?
Sample mean
t*
Sample standard deviation
Sample size
- 8. Multiple Choice
A 90% confidence interval for the mean speed driven by cars on Due West Road is given by (21, 45). What was the sample mean of this study?
12
24
33
None of these.
- 9. Multiple Choice
A 90% confidence interval for the mean speed driven by cars on Due West Road is given by (21, 45). What was the margin of error of this study?
12
24
33
None of these.
- 10. Multiple ChoiceFind the t* value for a 99% confidence interval with a sample of 23 people.1.7141.7112.064None of these.
- 11. Multiple ChoiceWhat is the t value associated with 90% confidence and a sample size of 15?1.3411.3451.7611.753
- 12. Multiple Choice
How do you calculate degrees of freedom?
n
n+1
1-n
n-1
- 13. Multiple Choice
Given the same mean, SD, and sample size, a confidence interval of 90% would be wider than a confidence interval of 95%
True
False
- 14. Multiple Choice
An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.
What is the point estimate?
75
105.2
10
0.90
- 15. Multiple Choice
If the 95% Confidence Interval for a population mean is (114.56, 125.54), then is it likely that the true population mean µ is greater than 130?
Yes
No
Not enough information
I have no idea what you're asking of me
- 16. Multiple Choice
A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was $139,048 to $154,144. Give a practical interpretation of the interval.
90% of the sampled CEOs have salaries that fell in the interval $139,048 to $154,144
We are 90% confident that the mean salary of all CEOs in the electronics industry falls in the interval $139,048 to $154,144.
There is a 90% chance that CEOs in the electronics industry have salaries that fall between $139,048 to $154,144
We are 90% confident that the mean salary of the sampled CEOs falls in the interval $139,048 to $154,144.
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