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- 1. Multiple Choice
What is the acronym we use to help remember the steps for calculating and interpreting a confidence interval?
ALARM
BLIZZARD
PANIC
SNOWDAY
- 2. Multiple Choice
2000 children were surveyed and the report that followed said, "With 98% confidence, between 20% and 50% of all parents make their children eat breakfast." What does 98% confidence mean in this situation?
We can be 98% confident that the method used to get the intervals always gives the correct answer
98% of all parents will make their kids eat breakfast
When used repeatedly, the method used to find the interval produces intervals which include the true proportion about 98% of the time
The kids were 98% confident that they ate breakfast that day.
- 3. Multiple Choice
Mr. Reinecke wants to estimate the proportion of seniors who will go to college next year with 96% confidence and a margin of error of no more than 5%. What size sample does he need to take?
422
419
410
400
- 4. Multiple Choice
Mrs. Soto polled 1000 adults and estimated with 90% confidence that the proportion of adults who have dessert after dinner is .75. Ms. Libner thinks that 90% confidence isn't enough and wants to do a 95% confidence. How would a margin of error for 95% compare with a ME for 90% if the same sample size was used?
It would be smaller because a higher confidence means a smaller MOE
It would be larger because a higher confidence means a larger MOE
It would be the same because the sample size is the same
Won't be able to tell without knowing the true parameter
- 5. Multiple Choice
You want to calculate a 98% confidence interval for a population mean with a sample of n = 20. What is the appropriate t*?
2.326
2.528
2.539
2.518
- 6. Multiple Choice
The heights of 5-year old boys are approximately normal. The mean height of a random sample of 37 5-year old boys is found to be 30 inches with a standard deviation of 3 inches. What is the standard error of x̄?
.493
1.32
5.77
1.96
- 7. Multiple Choice
Mrs. Soto wants to find the sample size needed to find with 95% confidence the mean amount of time her stats students spent on homework during the snow days. The population is approximately normal and the known standard deviation is 6 minutes. How large should the sample size be if she wants a margin of error of +- .5 minutes?
553
551
600
601
- 8. Multiple Choice
A survey of a random sample of 2500 adults who have a credit card found that 570 had a balance of $1000 or more on their credit card.
What would be the name of the confidence interval if constructed in this situation?
1 sample p interval for z
1 sample z interval for p
1 sample t interval for p
1 sample p interval for t
- 9. Multiple Choice
A survey of a random sample of 2500 adults who have a credit card found that 570 had a balance of $1000 or more on their credit card.
What would NOT be an condition we need to verify before constructing the interval?
np̂ ≥ 10 and n(1-p̂) ≥ 10
n ≥ 30
10% condition
random sample
- 10. Multiple Choice
A survey of a random sample of 2500 adults who have a credit card found that 570 had a balance of $1000 or more on their credit card.
What would be the margin of error if you had a 99% confidence?
0.022
0.0046
0.008
0.016
- 11. Multiple Choice
A survey of a random sample of 2500 adults who have a credit card found that 570 had a balance of $1000 or more on their credit card.
What symbol would you use to describe the parameter?
μ
p
p̂
x̄
- 12. Multiple Choice
Scores on the mathematics part of the SAT exam in a recent year were roughly Normal with mean 515 and standard deviation 114. You choose an SRS of 100 students and average their SAT Math scores. Suppose that you do this many, many times. Which of the following are the mean and standard deviation of the sampling distribution of x̄ ?
Mean = 515; SD = 114
Mean = 515; SD = 114/√100
Mean = 515/100; SD = 114/√100
Mean = 515/100; SD = 114/100
Mean = 515/100; SD = 114/√100
- 13. Multiple Choice
A newborn baby has extremely low birth weight (ELBW) if it weighs less than 1000 grams. A study of the health of such children in later years examined a random sample of 219 children. Their mean weight at birth was x̄ = 810 grams. This sample mean is an unbiased estimator of the mean weight in the population of all ELBW babies, which means that
In all possible samples of size 219 from the population, the mean of the values of will equal 810.
In all possible samples of size 219 from this population, the mean of the values of will equal μ
As we take larger and larger samples from this population, x̄ will get closer and closer to μ .
In all possible samples of size 219 from the population, the values of will have a distribution that is close to Normal.
The person measuring the children’s weights does so without any error.
- 14. Multiple Choice
Why is it important to check the 10% condition before calculating probabilities involving x̄?
To reduce the variability of the sampling distribution of x̄
To ensure that the distribution of x̄ is approximately Normal
To ensure that we can generalize the results to a larger population
To ensure that x̄ will be an unbiased estimator of μ.
To ensure that the observations in the sample are close to independent.
- 15. Multiple Choice
One reason for using a t distribution instead of the standard Normal curve to find critical values when calculating a level C confidence interval for a population mean is that
z can be used only for large samples
z requires that you know the population standard deviation
z requires that you can regard your data as an SRS from the population
z requires that the sample size is at most 10% of the population size
a z critical value will lead to a wider interval than a t critical value
- 16. Multiple Choice
A researcher wants to find a confidence interval estimate of the mean time it takes to complete an order over the phone at a call center for a large retail company. He has selected a random sample of 18 orders and recorded the time to complete the order. The sample mean time was 4.27 minutes and the sample standard deviation was 0.78 minutes. Assuming the conditions needed for inference are met, which of the following is the appropriate 98% confidence interval?
4.27 ± 2.326 ⋅ (0.78/√18)
4.27 ± 2.054 ⋅ (0.78/√18)
4.27 ± 2.552 ⋅ (0.78/√18)
4.27 ± 2.567 ⋅ (0.78/√18)
4.27 ± 2.567 ⋅ (0.78/√17)
- 17. Multiple Choice
Which of the following would not decrease the width of a confidence interval?
I. Increasing the sample size
II. Decreasing the degrees of freedom
III. Decreasing the confidence level
I only
II only
III only
I and II only
II and III only
- 18. Multiple ChoiceAn irate patient complained that the cost of a doctor's visit was too high. She randomly surveyed 20 other patients and found that the mean amount of money they spent on each doctor's visit was $44.80. The standard deviation of the sample was $3.53. Find the 95% confidence interval of the population mean.$43.15 - $46.45$44.53 - $48.21$42.65 - $48.25$43.15 - $48.25
- 19. Multiple ChoiceIn a study of 150 accidents that required treatment in an emergency room, 36% involved children under 6 years of age. Find the 90% confidence interval of the true proportion of accidents that involve children under the age of 6.0.331 - 0.4130.275 - 0.4330.295 - 0.4250.255 - 0.455
- 20. Multiple ChoiceAt a particular college, 78% of all students are receiving some kind of financial aid.The school newspaper selects a random sample of 100 students and 72% of the respondents say they are receiving some sort of financial aid. Which of the following is true?78% is a population and 72% is a sample.72% is a population and 78% is a sample78% is a parameter and 72% is a statistic72% is a parameter and 78% is a statistic
- 21. Multiple Choice
What does this symbol represent?population proportionparametersample proportionpopulation sample - 22. Multiple Choice
Including today, January 31, how many snow days have we had at WO in the 2018-2019 school year?
4
5
6
7
8
- Answer choicesTagsAnswer choicesTags