Home / Questions / A simple random sample of 80 customers is selected from an account receivable portfolio a...
A simple random sample of 80 customers is selected from an account receivable portfolio and the sample mean account balance is $1250. The population standard deviation σ is known to be $250. (8 points)
2. Construct a 95% confidence interval for the mean account balance of the population.
3. What is the margin of error for estimating the mean account balance at the 95% confidence level.
4. Construct a 95% confidence interval for the mean account balance of the population if the sample mean account balance is obtained from a random sample of 150 instead of 80.
5. Based on the results from a. and c., what can you say about the effect of a larger sample size on the length of the confidence interval at the same confidence level?
6. A simple random sample of 50 calls is monitored at an in-bound call center and the average length of the calls is 6.5 minutes. The population standard deviation σ is unknown. Instead the sample standard deviation s is also calculated from the sample and is found to be 4.5 minutes. (6 points)
7. Construct a 99% confidence interval (using the t-distribution) for the average length of inbound calls.
8. What is the margin of error at the 95% confidence level?
9. Do we need to make any assumption on the distribution of the length of in-bound calls at this call center? Why or why not?
1. According to a previous study, check out times at a supermarket are between 3 to 6 minutes (180 to 720 seconds.) A survey involving a random sample of customers of the supermarket is planned and the first order of business is to decide on an appropriate sample size. The 95% level of confidence will be used. (4 points)
2. What is the planning value for the population standard deviation to be used in the sample size formula for estimating the population mean check-out time?
3. How large should the sample size be if the desired margin of error is 25 seconds?
1. In a survey, the planning value for the population proportion is p* = 0.28. How large should the sample size for the survey be if the desired level of confidence is 95% and the desired margin of error is 0.035? (2 points)
Apr 06 2020 View more View Less
Nascent, Inc., acquires 60 percent of Sea-Breeze Corporation for $414,000 cash on January 1, 2012. The remaining 40 percent of the Sea-Breeze shares traded near a total v...
Jul 22 2020During the reaction between sodium thiosulphate with hydrochloric acid, If we increase the concentration of hydrochloric acid then speed of the reaction will: O Remain sa...
May 15 2021The mantra of Amazon.com CEO Jeff Bezos is “Get big fast.” As we saw in Chapter 13 on monopoly, one reason to “get big fast” is because in some industries the firm’s aver...
Apr 20 2020What is a curve's binormal vector? Give an example. How is this vector related to the curve's torsion? Give an example.
Jul 02 2021The Alliance Corp. expects to sell the following number of units of copper cables at the prices indicated, under three different scenarios in the economy. The probability...
Apr 24 2020________ are oxygen-releasing photoautotrophs.a. Spirochetesb. Methanogensc. Cyanobacteriad. Bacteriophages
Jul 07 2021The manager of a restaurant in a commercial building has determined that the proportion of customers who drink tea is 14%. What is the probability that in the next 100 cu...
Jun 22 2020A gas of unknown molecular mass was allowed to effuse through a small opening under constant-pressure conditions. It required 105 s for 1.0 L of the gas to effuse. Under ...
Aug 21 2021A private not-for-profit organization received a gift of $460,000 with purpose restrictions in 2013. In 2014 funds were expended for the purpose outlined in the gift, ho...
Jan 25 2020Dynamic Communication is a U.S. industrial company with several electronics divisions. The company has just released its 2013 annual report. Tables 18C and 18D present a ...
May 17 2020