NEW
Font size
WorksheetsAP Stats Confidence Intervals for Means
Total questions: 22
Worksheet time: 1hrs 3mins
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.
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
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
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 a condition we need to verify before constructing the interval?
np̂ ≥ 10 and n(1-p̂) ≥ 10
n ≥ 30
10% condition
random sample
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
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
A study found that in a sample of 44 subjects, 9 of them agree that children under 6 shouldn’t be taken to nice restaurants.
The 95% confidence interval for p is (0.082, 0.318). Interpret this interval.
95% of the time the proportion of people who believe children under 6 shouldn't be taken to nice restaurants will be between 8.2% and 31.8%.
The population proportion of people who believe children under 6 shouldn't be taken to nice restaurants is between 8.2% and 31.8%.
The probability that the proportion of people who believe children under 6 shouldn't be taken to nice restaurants will be between 8.2% and 31.8% is 95%.
Based on this sample, I am 95% confident that the proportion of people who believe children under 6 shouldn't be taken to nice restaurants is between 8.2% and 31.8%.
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
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
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
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
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
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)
