Dr. Caras was characterizing a cytochrome (an iron containing protein) from a ne

Question

Dr. Caras was characterizing a cytochrome (an iron containing protein) from a new strain of bacteria. He obtained the following values in eight measurements of the percent iron in the protein:      0.5507%, 0.5503%, 0.5498%, 0.5495%, 0.5613%, 0.5495%, 0.5508%, 0.5494%

Calculate the mean (x) and standard deviation (s) for these results.

Use the Grubbs test to determine if one of these values is an outlier. What is the value of Gcalculated? Should this potential outlier be rejected with 95% confidence? Critical values of G can be found in the following table.

Explanation / Answer

Here mean strain of bacteria x = sum of all numbers/ total numbers = 0.5514 %

Standard deviation s = 0.0040 %

Test statistic

G = (xmax -x)/s = (0.5613 - 0.5514)/ 0.0040 = 2.475

95% confidence value for outlier for n = 8 and alpha = 0.05

Gcritical = 2.1266

so here we see that G > Gcritical , so we reject that the there is no outlier . the value of 0.5613 is and outlier.

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