Compare your answers.

  1. Three separate companies conducted similar surveys related to internet use.

     Company ACompany BCompany C
    Sample Size
    756
    1020
    904


    Assuming all other factors were similar, which company do you expect had

      1. the smallest margin of error?

        Company B should have had the smallest margin of error because they used the largest sample.


      1. the smallest confidence interval?

    Company B should also have had the smallest confidence interval because they used the largest sample.
  2. Three separate companies conducted similar surveys related to food preference.

     Company DCompany ECompany F
    Confidence
    Level
    19 out of 20
    9 out of 10
    49 out of 50


    Assuming all other factors were similar, which company do you expect had

      1. the smallest margin of error?

    Company E should have had the smallest margin of error because they used the lowest confidence level.

    1. the smallest confidence interval?

      Company E should have had the smallest confidence interval because they used the lowest confidence level.


  3. Three separate companies conducted similar surveys related to vacation
    activity.

     Company GCompany HCompany I
    Confidence
    Level
    90%
    95%
    98%
    Margin of Error
    4.2%
    4.9%
    5.8%

    Explain why it is difficult to compare the claims of the companies.

    Company G had the smallest confidence interval, but you are less sure the true value would fit within this interval because of the lower confidence level. Company I had the largest confidence interval, however, the true value is more likely to have fallen within that interval because a higher confidence level was used.
For further information about confidence intervals see pp. 295 - 301 of Principles of Mathematics 11.

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