Q 1
The following information is collected from students as they leave the campus bookshop during the first week of classes.
State the level of measurement for the variables given below.
Gender Answer 1
Number of textbooks purchased Answer 2
Amount of time spent shopping in the bookshop Answer 3
Name of degree Answer 4
Q 2
Suppose that an energy company wants to estimate its mean waiting time for natural gas installation to within 5 days with 95% confidence. The company has access to previous data and they know that the standard deviation is 30 days.
How large a sample is necessary?
Sample should be at least Answer
Q 3
The fill amount of bottles of soft drink is normally distributed with a mean of 2.0 litres and a standard deviation of 0.05 litres. If you select a random sample of 25 bottles, what is the probability that the sample mean will be:
above 2.01 litres?
Select one:
a. 0.0228
b. 0.1587
c. 0.0143
d. 0.9969
Q4
The personnel manager of a large corporation wishes to study absenteeism among clerical workers at the corporation's central office during the year. A random sample of 25 clerical workers indicated that 48% were absent for more than 10 days. We are interested in a 99% confidence interval estimate of the population proportion of clerical workers absent for more than 10 days. Which of the following is the correct 99% confidence interval:
Select one:
a. (0.28, 0.68)
b. (0.22, 0.74)
c. (0.32, 0.64)
Q5
A 95% confidence interval for the proportion of a population is computed from a random sample and found to be . We may conclude:
Select one:
a. there is a 95% probability that the true proportion is 50% and there is a 95% chance that the true margin of error is 10%.
b. all of the other answers are correct.
c. if we took many, many additional random samples and from each computed a 95% confidence interval for , approximately 95% of these intervals would contain .
d. there is a 95% probability that is between 60% and 40%.
Q6
The Nielsen company regularly conducts research into consumer confidence. It reports that in an online survey of Australian consumers conducted early in 2011, 68% of the respondents were trying to save on gas and electricity expenditure. Consider a follow-up study focusing on the latest calendar year. What sample size is needed to estimate the population proportion of Australian consumers who are trying to save on gas and electricity expenditure to within 2 percentage points with 95% confidence?
Sample should be at least Answer
Q7
The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The standard deviation is 80 hours. A random sample of 64 light bulbs indicated a sample mean life of 350 hours.
90% confidence interval estimate for the population mean life of light bulbs in this shipment lies between:
Select one:
a. (330.4 hours and 369.6 hours)
b. (324.2 hours and 375.8 hours)
c. (333.6 hours and 366.4 hours)
d. (270 hours and 430 hours)
Q8
A market researcher for a consumer electronics company wants to study the television viewing habits of residents of a particular area. A random sample of 41 respondents is selected, and each respondent is instructed to keep a detailed record of all television viewing in a particular week. The results showed a mean viewing time of 15.3 hours and a sample deviation of 3.8 hours.
90% confidence interval estimate for the population mean amount of television watched per week lies between:
Select one:
a. (11.5 hours and 19.1 hours)
b. (14.30 hours and 16.30 hours)
c. (13.70 hours and 16.90 hours)
d. (14.10 hours and 16.50 hours)