1)

Using graphite furnace atomic absorption spectrometry (GFAAS), the mean cadmium(Cd²⁺) content value in a homogenized sample of 40zebramussles was found to be8.80 ppbCd²⁺with a standard deviation(s)of0.53 ppbCd²⁺. Assume thatsis a good approximation of.

Calculate the 90% and 95% confidence intervals (CI) for two analyses of this homogenizedsample.

90%CI= 8.80 ___________ ppb . 95%CI= 8.80 ___________ ppb.

Calculate the 90% and 95% confidence intervals (CI) for five analyses of this homogenizedsample.

90%CI= 8.80 ___________ ppb . 95%CI= 8.80 ___________ ppb.

2)

Calculate the mean and 90% confidence interval for the data set. Report your answer with the correct number of significantfigures.

Sample . Value

1 9.0560

2 . 9.0730

3 . 9.0670

4 . 9.0590

5 . 9.0590

6 . 9.0600

mean: ______________ ______________

3)

The weight percent of silicon in six different rock samples, each containing different amounts of silicon, was measured by two different methods. The results are given in thetable.

Sample . Method A Si wt% . Method B Si wt%

1 . 11.570 . 11.550

2 . 15.380 . 15.280

3 17.950 17.900

4 22.840 22.810

5 25.110 25.150

6 27.070 27.030

Determinet_calc

t_{calc=____________.}

Determinet table at the 95% confidence level. A list oft values can be found in theStudent'sttable.

t _table= _________.

Are these methods significantly different at the 95% confidencelevel?

4)

A young researcher was evaluating a standard method for determining the methylmercury content in blue fin tuna using high performance liquid chromatography (HPLC). She determined the standard deviation(s)for the method to be0.35 ppb and assumed thatswas a good approximation of.

As a test, she used this method to evaluate the methylmercury content in a National Institutes of Standards and Technology (NIST) standard and determined the unknown amount to be within0.19 ppb () of the known mean with 99% probability. How many replicate measurements of the NIST standard did the researcherperform?

N=__________.