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    This seems a stupid question but why does it equal to 6.86 and not 5?
    I know 5 would just give me 1.96 again but I dont understand the 6.86Name:  s3 q13.png
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    (Original post by RK1998)
    This seems a stupid question but why does it equal to 6.86 and not 5?
    I know 5 would just give me 1.96 again but I dont understand the 6.86Name:  s3 q13.png
Views: 62
Size:  97.7 KB

    \displaystyle \frac{141.86 - 128.14}{2} = 6.86.
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    (Original post by Zacken)
    \displaystyle \frac{141.86 - 128.14}{2} = 6.86.
    So it's just the difference of the intervals divided by 2.
    Thank you so much

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    (Original post by RK1998)
    So it's just the difference of the intervals divided by 2.
    Thank you so much
    Yes, you know the width of an interval is given by 2 \times z \times \frac{\sigma}{\sqrt{n}} but the width here is the difference of the limits.

    So 2 \times z \times \frac{\sigma}{\sqrt{n}} = 13.72 and then dividing both sides by 2 gets you your answer.

    You're very welcome.
 
 
 
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