Oromia State University College of Finance and Management Studies Department of Management Business Statistics Group and Individual Assignment

Oromia State University
College of Finance and Management Studies

Department of Management
Business Statistics Group and Individual Assignment
Group Assignment
1. Suppose for the entertainment industry the sample variance of the wages for full-time
employees are birr 1,764 per hour. A random sample of 196 employees from
entertainment industry reveal a mean wage of birr 85 per hour ……Interpret the
result……………………
a) Construct a 95% confidence interval and determine lower and upper limit.
b) Construct 99% confidence interval and determine lower and upper limit.
c) If instead of 196 employees, if the entertainment industry took 25 employees. Construct
90% confidence interval.
d) Based on ‘C’. Construct 95% confidence interval and determine lower and upper limit.
2. The management of a supermarket needs to estimates the average daily demand for milk.
The following data shows the sample demand for the last 15 days in liter.
Demand for milk: 60, 59, 45, 62, 50, 68, 57, 80, 65, 58, 79, 70, 42, 85, and 65.
a) Construct a 90% confidence level and interpret the result.
b) Determine the lower and upper limit demand of milk at 95% confidence level.
3. A study is conducted in a company that employs 800 engineers. A random sample of 50
engineers reveals that the average sample age is 34.3 years. Historically, the population
standard deviation of the age of the company’s engineers is approximately 8 years.
a) Construct a 98% confidence interval to estimate the average age of all the engineers in
this company.
4. Ato Tola is running for college dean election and to check the election results he made
his own election pool prior to the final election. Accordingly the result shows that a
random sample of 100 voters 58 will vote him. Develop a 95% confidence interval for the
population proportion who will vote for Ato Tola. Can he conclude that he will win the
election?
5. A person suspects that a candy company is misrepresenting the weight of their candy bar,
and that its weight is less than the advertised 100 grams. The standard deviation of the
bar’s weight is known to be 12 grams. The person plans to weigh 100 randomly selected
bars and obtains an average weight of 98.5 grams. What conclusion do we reach at a 5%
level of significance?
Oromia State University
College of Finance and Management Studies
Department of Management
Business Statistics Group and Individual Assignment
6. A researcher wants to study the working conditions in the textile industry; accordingly
the researcher made a census in the industry and the survey shows 5000 employees. How
many employees have to be taken as a sample at 95% confidence level?
7. Health minster conducted a national survey to determine the extent to which employers
are promoting health and fitness among their employees. One of the questions asked was,
does your company offer on-site exercise classes? Suppose it was estimated before the
study that no more than 40% of the companies would answer yes. How large a sample
would health minster have to take in estimating the population proportion to ensure a
98% confidence in the results and to be within 0.03 of the true population proportion?
Individual Assignment
8. The manager of Bune Café and Restaurant believe that the average waiting time to serve
a customer is 5 minutes. To provide fast service Bune Café and Restaurant hires
additional waiters. The manager of Bune wants to analysis the effect of hiring additional
waiters and he has taken a random sample of 49 customers and find out sample mean
time waiting of 4 minutes with a sample standard deviation of 2 minute.
a) Can the manager conclude hiring additional waiters will change waiting time? Test at
0.02 level of significance.
b) Can the manager conclude hiring additional waiters will reduce waiting time? Test at
0.05 level of significance.
c) Based on the given information above, the manager took 25 customers instead of 100
customers. Will change the waiting time? Test at 0.05 level of significance.
d) Based on ‘C’ will reduce the waiting time? Test at 0.01 level of significance.
9. A group of young businesswomen wish to open a high fashion boutique in a vacant store,
but only if the average income of households in the area is more than Birr 45,000 per
annum. A random sample of 9 households showed the following results.
Income per year (Birr):- 48,000, 44,000, 46,000, 43,000, 47,000, 46,000, 44,000, 42,000,
45,000.
a) Can they open the boutique in the area or not? Test at 0.02 level of significance.
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