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Analytical Chemistry: Analyses of samples of Hg in fish give the following data for...

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whitetie | Student, Undergraduate | eNotes Newbie

Posted September 3, 2013 at 4:37 PM via web

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Analytical Chemistry:

Analyses of samples of Hg in fish give the following data for three trials:

ppm Hg = 1.80, 1.58, 1.64

a) Calculate the 95% CI for the mean when s is a good estimation of σ and is equal to 0.10. 
Answer: 1.67 (+/- 0.11) ppm.


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jerichorayel | College Teacher | (Level 1) Senior Educator

Posted October 8, 2013 at 8:14 AM (Answer #1)

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 `Mean = bar x = (sum (x))/n`

n = number of values/population = 3

`bar x = (1.80 + 1.58 + 1.64)/(3) `

`bar x = 1.67 `

Standard deviation = `s = sqrt((sum (x-bar x))/(n-1))`

`s =sqrt((sum (x-bar x)^2)/(n-1)) `

`s = sqrt(((1.80-1.67)^2 + (1.58-1.67)^2 + (1.64-1.67)^2)/2) `

`s = 0.11 `

*If s is a good estimation of sigma

Answer = 1.67 (+/1 0.11) ppm


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