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They indicated that the estimate was based on a sample of 100 people and that the margin of
error was 2.8. Assuming a 95% confidence level was used, calculate the value of the standard
error.
sample mean is computed. What is the probability that the sample mean is within 3 units of the
true mean if the standard error is 1.8?
offered by the store. In a random sample of 400 customers, what is the probability that between
156 and 240 customers will be satisfied with the service offered by the store?
1. A two-digit number between 10 and 99 inclusive is written down at random. What is the probability that it:
a) Is divisible by 5?
b) Is divisible by 9?
c) Is greater than 40?
d) Is a perfect cube?
Of the population of customers of a store, a proportion of 0.4 are not satisfied with the service offered by the store. In a random sample of 400 customers, what is the probability that between 156 and 240 customers will be satisfied with the service offered by the store?
A group of automotive engineers decided to conduct a study of its school buses and found that for 30 buses, the average stopping distance of buses traveling 50 miles per hour was 251 feet. The standard deviation of the population was 3.2 feet. Find the 99% confidence interval of the mean.
a. Margin of error
b. Confidence interval
c. Would a bus stopping at a distance of 249.5 feet be smaller than average? Explain.
2. The width of white board markers manufactured by a company is approximately normally distributed with a mean of 12 mm (millimetres) and a standard deviation of 4 mm. If a random sample of size 16 white board markers is selected, what is a) the distribution of the mean? b) the probability that the sample mean is less than 15.6 mm? c) the probability that the sample mean is between 12.8 mm and 13.2 mm?
Using z-table, find the critical value(s) for each.
1. ∝= 0.05, two-tailed test
2. ∝= 0.01, left-tailed test
3. ∝= 0.005, right-tailed test
4. ∝= 0.01, right-tailed test
5. ∝= 0.05, left-tailed test
6. ∝= 0.02, left-tailed test
7. ∝= 0.05, right-tailed test
8. ∝= 0.01, two-tailed test
9. ∝= 0.04, left-tailed test
10. ∝= 0.02, right-tailed test
A. For each conjecture, state the null and alternative hypothesis.
1. The average age of community college students is 18.6 years.
2. The average income of accountants is Php 107,285.54.
3. The average age of attorneys is greater than 25.4 years.
4. The average score of high school basketball games is less than 88.
5. The average pulse rate of male marathon runners is less than 70 beats per minute.
6. The average cost of a DVD player Php 3,997.50.
7. The average weight loss for a sample of people who exercise 30 minutes per day for 6 weeks is 8.2 pounds.
8. The average age of graduating students in college is 21.5 years.
9. The average salary of Public-School Teacher (entry level) is Php 21,899.
10. The average time spent using cellphone is 4 hours and 30 minutes.
