WorksheetsProb/Stats Unit 6 Quiz Corrections Assignment
Total questions: 15
Worksheet time: 1hrs 15mins
Find the margin of error for the mean number of telephone calls directed by a local telephone company if s = 4.5 minutes, n = 420, and we want to be 95% confident.
0.020
0.432
0.009
0.117
A sample of 31 people were randomly selected from among the workers in a shoe factory. The time taken for each person to polish a finished shoe was measured, and the sample mean was 2.2 minutes with a sample standard deviation of 0.72 minutes. Construct the 90% confidence interval for the mean time to polish a shoe.
(1.98, 2.42)
(1.87, 2.53)
(1.95, 2.45)
(1.90, 2.50)
Scores on a certain test are normally distributed with a VARIANCE of 56. A researcher wishes to estimate the mean scores achieved by all adults on the test. Find the sample size needed to assure with 98% confidence that the sample mean will not differ from the population mean by more than 3 points.
34
1892
102
14
A group of 59 randomly selected students have a mean score of 38.8 with a standard deviation of 5.8 on a placement test. What is the 90% confidence interval for the mean score of all students taking the test?
(37.0, 40.6)
(37.3, 40.3)
(36.9, 40.7)
(37.5, 40.1)
For a sample with 66 observations, the mean is 33 and the standard deviation is 8.5. Use a 95% confidence level to find the margin of error for mean.
1.86
1.76
2.09
4.25
In a sample of 170 observations, there were 75 people who liked pizza. Find the margin of error for the proportion of people who like pizza given a 95% confidence level.
0.1310
0.0746
0.0028
0.0671
A survey of 300 union workers in New York State reveals that 112 favor the Independent candidate for governor. Construct the 98% confidence interval for the true proportion of all New York State union workers who favor the Independent candidate.
(0.344, 0.402)
(0.301, 0.0445)
(0.316, 0.430)
(0.308, 0.438)
Find a 95% confidence interval for proportion if n=61, x=23.
(0.275, 0.479)
(0.254, 0.500)
(0.255, 0.499)
(0.274, 0.480)
Of 92 randomly selected adults, 73.9% have health insurance. Find a 90% confidence interval for the true proportion of all adults in the town who have health insurance.
0.632 < p < 0.846
0.664 < p < 0.814
0.644 < p < 0.442
0.621 < p < 0.857
A survey of shoppers is planned to see what percentage use credit cards. Prior surveys suggest 86% of shoppers use credit cards. How many shoppers should be surveyed for a 95% confidence level if we want to be within 2% of the true population proportion?
1157
1156
814
815
A pollster wishes to estimate the true population proportion of U.S. voters who agree with candidate A. How many voters should be surveyed in order to be 90% confident that the true proportion is within 7%?
196
197
139
138
Find the critical value, Ch-squared left corresponding to a sample size of 4 and a confidence level of 98%.
11.345
0.297
0.115
13.277
The mean systolic blood pressure for a random sample of 25 women aged 18-24 is 115.9 mm Hg, and the standard deviation of the sample is 12.8 mm Hg. Construct a 90% confidence interval for the population standard deviation.
(10.22, 16.40)
(10.43, 16.74)
(10.61, 17.20)
(10.39, 16.85)
How many people must be surveyed if you want to be 99% confident that the sample standard deviation, s, is within 5% of the population standard deviation?
767
1335
3148
5457
Evaluate t* for a confidence interval about the mean with a confidence level of 99% and a sample size of 17.
2.898
2.583
2.921
2.567
