In: Statistics and Probability
The CEO of a large corporation asks
his Human Resource (HR) director to study absenteeism among...
The CEO of a large corporation asks
his Human Resource (HR) director to study absenteeism among its
executive-level managers at its head office during the year. A
random sample of 30 executive-level managers reveals the
following:
Absenteeism: Sample mean = 7.3 days, Sample standard deviation =
6.2 days
18 mid-level managers out of the 30 randomly selected mid-level
managers cite stress as a cause of absence.
- Construct a 90% confidence interval estimate for the mean
number of absences for mid-level managers during the year.
- Construct a 98% confidence interval estimate for the population
proportion of mid-level managers who cite stress as a cause of
absence.
- What sample size is needed to have 95% confidence in estimating
the population mean absenteeism to within ±1.5 days if the
population standard deviation is estimated to be 8 days?
- How many mid-level managers need to be selected to have 99%
confidence in estimating population proportion of mid-level
managers who cite stress as a cause of absence to within
±0.075 if no previous estimate is available?
4) Sam
and Hannah, own a restaurant in Edison, New Jersey, and want to
study the dining characteristics of their customers. They decide to
focus on two variables: the amount of money spent by customers and
whether customers order dessert. The results from a sample of 61
customers are as follows:
Amount spent: Sample mean = $45.83, Sample standard deviation =
$6.27
17 out of the randomly selected 61 customers, purchased
dessert.
- Construct a 98% confidence interval estimate for the population
mean amount spent per customer in the restaurant.
- Construct a 90% confidence interval estimate for the population
proportion of customers who purchase dessert.
Their rival Jim owns a competing
restaurant. He wishes to conduct a similar survey in his
restaurant. However, he does not have access to the information
that Sam and Hannah have obtained from the survey they conducted.
Jim wants to know the following:
- What sample size is needed to have 99% confidence of estimating
the population mean amount spent in his restaurant to within
±$2.60, assuming that the population standard deviation is
estimated to be $9?
- How many customers need to be selected to have 95%confidence of
estimating the population proportion of customers who purchase
dessert to within±0.04?