(1) F. P. A. Cal Culator obtained the following results for replicate determinat

Question

(1) F. P.

A.    Cal Culator obtained the following results for replicate determinations of calcium in limestone: 14.35%, 14.41%, 14.40%, 14.32%, and 14.37%. Calculate the confidence interval at the 95% confidence level.

B.     A new procedure for determining trace amounts of zinc in vegetables was evaluated by using it to determine the zinc content of a NIST standard sample, with the following results: 0.083, 0.088, 0.087, and 0.086 ppm Zn. The certified value of the standard sample is 0.082 ppm Zn. Is there a significant difference between the mean of the results and the certified value?

Explanation / Answer

Q1.

AVG = sum (14.35%, 14.41%, 14.40%, 14.32%, and 14.37%) / 5

AVG = 14.37

STDEv = sqrt(sum(x-m^2)..)

STDEV =0.036742

now

interval

AVG +/- Z(95%)*STED/sqrt(n)

Z for both tails at 95% --> 1.96

so

Upper limit = 14.37 + 1.96*0.036742/(sqrt(5)) = 14.4022

Lower limit = 14.37 - 1.96*0.036742/(sqrt(5)) = 14.3377

therefore

14.3377% < Level < 14.4022%

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