1) To determine the number of picograms/gram of hexacholohexanes in sea sediment

Question

1) To determine the number of picograms/gram of hexacholohexanes in sea sediments two separate chromatography procedures were used. Determine if the standard deviations are different between the methods. Second determine if the methods differ significantly at the 95% confidence level? (show your work) Method Concentration (pg/8) Standard Deviation(p/e)n Conventional New Procedure 34.4 42.9 3.6 4.1 6 2) Calculate the percentage of light bulbs that will last between 795.0 and 1042.0 hours using the following data. (show your work) 845.2 94.2 4768 mean 3) Consider the data set below, which value(s) should be rejected based on the Grubs test. Excel may be used for calculation if the data and calculation are clearly labeled. You may print a copy of the worksheet and attach it with this cover sheet 203, 219, 202, 196, 204, 208, 199,198, 209, 203, 173, 198 4) The CdSe content (g/L) of nanocrystals was measured by two methods for six different samples. Do the two methods differ significantly at the 95% confidence level? See data below: (Excel may be used for calculation if the data and calculations are clearly labeled. See Figure 4-8 in your text as an example. Attach the printout with this cover sheet.) Method 1 Method 2 Sample Anocid Stripping Atomic absorption 0.88 1.15 1.39 0.99 1.11 1.31 0.83 1.04 1.22 0.91 1.09 1.31

Explanation / Answer

As per company policies I am answering question one only.

2)

mean= 845.2
sd= 94.2
n= 4768

P(795 < X < 1042)
= P(X<1042) - P(X<795)

I know that, z = (X-mean)/(sd/sqrt(n))
z1 = (795-845.2)/94.2/sqrt(4768))
z1= -36.7977
z2 = (1042-845.2)/94.2/sqrt(4768))
z2= 144.2588

hence,
P(795 < X < 1042)=
= P(Z<144.2588) - P(Z<-36.7977)
= NORMSDIST(144.2588) - NORMSDIST(-36.7977)
1.0000
100%

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