Using graphite furnace atomic absorption spectrometry, the mean cadmium (cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 7.50 ppb cd2 with a standard deviation (s) of 0.52 ppb cd2 (assume that s is a good approximation of σ). calculate the 90% and 95% confidence intervals (ci) for: (a) two analyses and (b) five analyses of this homogenized sample.

Part A1:

Given that the mean cadmium (cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 7.50 ppb cd2 with a standard deviation (s) of 0.52 ppb cd2

The 90% confidence interval for a sample of size n, with sample mean and a standard deviation of s is given by:



Thus, the 90% confidence intervals (ci) for two analyses is given by:




Part A2:

Given that the mean cadmium (cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 7.50 ppb cd2 with a standard deviation (s) of 0.52 ppb cd2

The 95% confidence interval for a sample of size n, with sample mean and a standard deviation of s is given by:



Thus, the 95% confidence intervals (ci) for two analyses is given by:



Part B1:

Given that the mean cadmium (cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 7.50 ppb cd2 with a standard deviation (s) of 0.52 ppb cd2

The 90% confidence interval for a sample of size n, with sample mean and a standard deviation of s is given by:



Thus, the 90% confidence intervals (ci) for five analyses is given by:




Part B2:

Given that the mean cadmium (cd2 ) content value in a homogenized sample of 40 zebra mussles was found to be 7.50 ppb cd2 with a standard deviation (s) of 0.52 ppb cd2

The 95% confidence interval for a sample of size n, with sample mean and a standard deviation of s is given by:



Thus, the 95% confidence intervals (ci) for five analyses is given by:

The correct answer is c