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Old 05-04-2012
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Stats Calculating the 95% Confidence Interval?

100 students took a medical school exam and the average score was 110 with a standard deviation of 20. Which of the following is the best estimate of the 95% confidence interval for the sample?

a. 70 to 130
b. 70 to 150
c. 90 to 130
d. 105 to 115
e. 106 to 114
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E) 106-114


Mean = 110
SD = 20
n (sample size) = 100

For 95%, use Confidence Interval of 1.96 or 2 (to simplify calculation)

Mean +/- CI * (SD/ sqrt of n)
= 110 +/- 2*(20/sqrt100)
= 110 +/- 2*(20/10)
= 110 +/- 2*(2)
= 110 +/- 4
= 110-4 to 110+4
= 106-114
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Quote:
Originally Posted by Hope2Pass View Post
E) 106-114


Mean = 110
SD = 20
n (sample size) = 100

For 95%, use Confidence Interval of 1.96 or 2 (to simplify calculation)

Mean +/- CI * (SD/ sqrt of n)
= 110 +/- 2*(20/sqrt100)
= 110 +/- 2*(20/10)
= 110 +/- 2*(2)
= 110 +/- 4
= 110-4 to 110+4
= 106-114
I see someone is revising biostats hehe =)

I got this one wrong, only 23% got it right in Kbank, I believe its worth posting in here.
Great explanation!
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Quote:
Originally Posted by DocSikorski View Post
I see someone is revising biostats hehe =)

I got this one wrong, only 23% got it right in Kbank, I believe its worth posting in here.
Great explanation!
Thanks!

I remember doing a question on CI in the Qbank about 2-3 weeks ago and I got it wrong...so I knew my stuff and made sure I don't make same mistake twice
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Old 05-04-2012
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damn, i immediately jumped at B :/ lol
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Old 05-04-2012
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Answer B
70 - 150
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Biostatistics-Epidemiology, Step-1-Questions

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