ARC
Week+7_Practice_problems

Week+7_Practice_problems - Practice Problems Week 7...

Info icon This preview shows pages 1–3. Sign up to view the full content.

Practice Problems Week 7 Chi-square problems Question 1 The manager of an insurance company’s 24 hours emergency help line wishes to understand whether responsiveness to customer calls varies according to the time of day. The manager takes a random sample of 90 customer calls, and for each call determines the work shift during which the call was made, and whether the call was answered within 10 seconds. The data appears in the table below. Observed Work Shift Morning Mid-day Afternoon Night Graveyard Total Responsivenes s 5:00 - 10:00 10:00 - 14:00 14:00 -19:00 19:00 - 00:00 0:00 - 5:00 Answered in 10 seconds 19 14 12 10 4 59 Not Answered in 10 seconds 4 15 8 3 1 31 Total 23 29 20 13 5 90 a) Being careful to state your conclusions, and using a level of significance of = 5%, test whether responsiveness is independent of work shift. b) Using this question to provide examples, explain the difference between a type 1 and type 2 error.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Question 2 When a customer moves out of a building, the phone lines are usually left intact by the phone company, ready to be activated when the next customer moves in. Usually these activations are effective but sometimes they are not. If the new customer has to report a fault within seven days of having a phone service activated, the activation is considered ineffective. The Operations Manager of telephone company is keen to better understand why some activations are ineffective. Some technicians have suggested that one factor might amount of time that service was inactive – that is, the number days between the previous customer leaving and the new customer wanting the service activated. To investigate these suggestions, the Operations Manager draws a random sample of 191 recent activations. For each activation, records are interrogated to find out how long the phone service was inactive and whether or not the new customer reported a fault within seven days of the activation. The data is summarised in the table below.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.
  • Spring '14
  • Garofalo,LB
  • Variance, Statistical hypothesis testing, Randomness, Statistical significance, SMAC, age based market

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern