Show:
Conditions
1&2 sample z test
1&2 sample z interval
Miscellaneous
p-value
100
Should you check conditions for both samples when performing a 2-sample z-test?
Yes
100
At a man made lake in central Pennsylvaina, an average of 50 gallons of water flow over the spillway every minute with a standard deviation of 15 gallons. Distribution assumed to be normal. What is the probability that for any randomly chosen minute, fewer than 20 gallons of water goes over the spillway?
.0228
100
Two random samples of American adults are taken and religious affiliations recorded. Of the 200 adults in the first sample, 66 are Christians. Of the 140 in the second sample, 12 are Buddhists. Assuming the samples are independent, what would the confidence interval be?
(.1635,.32511)
100
How many people should be surveyed to find out whether AP* Stats students do their homework? A previous record indicates 60% did their homework with a 5% margin of error and 95% confidence.
369 students
100
When do you reject the null hypothesis?
When the p-value is less than the alpha level
200
What is used to eliminate bias and allow the sample to be more representative of the population?
Randomization Assumption
200
A manufacturer of brick pavers maintains that 80% of the pavers produced by his company meet the standard 15-inch length. Of a random sample of 51 pavers 27 meet the standard. Does this show that the proportion of pavers that meet the standard is less than the manufacturer's claim?
Yes the proportion of pavers that meet the standard is less that 80%. p-value is 0.
200
Based upon a random sample of 30 seniors in a high school, a guidance counselor finds that 20 of the 30 seniors plan to attend an institution of higher learning. A 90% confidence interval from this yields (.5251,.80823) What would be the correct interpretation for this interval?
We can be 90% confident that 52.51% to 80.82% of seniors at this high school plan to attend an institution of higher learning.
200
With an alpha level of 5% what is the power of a test against an alternative for which the probability of Type II error is 3%?
97%
200
What is the p-value for a z-score of -2.57?
.0051
300
What condition uses the formulas np>10 and nq>10?
success failure
300
Double Jeopardy!!! Of 75 randomly selected men 30 had walked for exercise. Of 75 randomly selected women 36 had walked for exercise. Assume the samples are independent. Is there evidence to show a significant difference in the proportion of men to women who walk for exercise?
There is insufficient evidence with a p-value of .324. you fail to reject the null that there is not a significant difference between men and women walking for exercise.
300
A random sample of construction workers was taken in a large city. Of 150 workers sampled, 16 were unemployed. What would be the 90% confidence interval for the proportion of unemployed construction workers in this city.
(.0652,.1482)
300
A no appointment haircutter advertises an average wait time of 15 minutes for customers. Customers have claimed that the actual wait time is 30 minutes. A random sample of 30 customers was selected and wait times recorded to determine the true wait time. The power of the test is 50%, how do you increase the power?
Increase sample size and alpha level.
300
What is the p-value for a z-score of 3.90?
1
400
Men's blood pressure is tested every 6 months, twice. The sample was obtained randomly and it is assumed to have sufficent sample size. The researchers want to compare the proportion of people with high blood pressure from each test to see if there is any change over time. Is a two proportion z test apporpriate?
No independence is not met
400
Two different Internet sites claim to offer the lowest hotel rates for major U.S. cities. To test this claim a consumer group randomly selects 50 hotels and checks the rate charged on both sites. To determine if there is a significant difference in rates between these two sites what test is appropriate?
Matched pairs test
400
Your local newspaper polls a random sample of 33o voters finding 144 who say they will vote "yes" on the upcoming school budget. What would be the 95% confidence interval for actual sentiment of all voters?
(.381,.491)
400
A newlywed couple is trying to choose one of two neighborhood supermarkets for their grocery shopping. They decide to randomly select 20 items, check prices at each store, and then conduct a test to determine if one store is significantly less expensive than the other. What test should they conduct?
Matched pairs
400
Past records show that on average 65% of visitors will spend money in the gift shop at a local attraction on any given day. If there are 525 visitors on any given day what is the probability that at least 70% of these visitors purchase something in the gift shop?
the p-value is .0082
500
Are the conditions for a z-interval different than a 1-proportion z-test?
No
500
A random sample of adults is taken in a rural county. Of the 120 adults sampled,16 live in poverty. The poverty rate for the entire state is 8.9%. Is there statistical evidence to show that the poverty rate of this county is higher than that of the state?
Since 1.706 is greater than 1.645 there is sufficient evidence at the alpha level of 5% to show that the poverty rate of the county is higher than the state.
500
An experiment finds that 27% of 53 subjects report improvement after using a new medicine. Using this data what would be a 95% confidence interval of cure rate?
(.1505,.3895)
500
Double Jeopardy!!! In a very large school district, the food services administrator whishes to determine the proportion of students who will buy lunch to within plus or minus .03. Using the most conservative estimate for p, how may students should this administrator survey to have 90% confidence?
752
500
An aspirin claims that 4 out of 5 doctors recommend its product. A consumer advocacy group believes the proportion is lower. To test the claim, a random sample of 50 doctors is selected, and 35 recommend this manufacturer's product. What would be the p-value?
.039