Tap water is measured for arsenic and found to have a mean signal of 0.0061. Next, a small amount of Arsenic is spiked i

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Tap water is measured for arsenic and found to have a mean
signal of 0.0061. Next, a small amount of Arsenic is spiked into
the tap water such that the new value is 0.700 ppb higher than
before. The mean signal from this new low-level concentration is
0.0447, with a standard deviation of 0.00560. What is the Lower
Limit of Quantitation?
(Hint: estimate slope as fraction numerator triangle Y over
denominator triangle X end fraction , where triangle Y is the
difference between the low level spike and the blank signals; and
triangle X is the concentration change between the spiked and
unspiked sample)