Quality Assurance Flashcards
Quality Assurance
what we do to get the right answer and be confident it is the right answer
10 red markers are sampled every hour as they exit the final step of production before mixing and packaging
sampling requirements
accuracy
how close to the true value you are
what ways is accuracy measured in?
mean, % error
precision
how well replicate measurements agree with one another
what ways is precision measured in?
confidence interval, standard deviation, relative standard deviation (st. dev. / mean), standard uncertainty
false positives
result is positive when it is actually negative
false negatives
result is negative when it is actually positive
selectivity
extent to which a method can distinguish the analyte from everything else in the sample
sensitivity
method or instrument response to changes in sample concentration; change sample concentration a small amount and observe a big change
what are the three types of blanks?
instrument, reagent, method/solvent
instrument blank
nothing in the instrument
what does an instrument blank tell us?
observes the electronic noise
reagent blank
one reagent at a time is put into the instrument
method/solvent blank
the solvent by itself goes through every step of the experiment
what is the purpose of the method/solvent blank?
shows any problem with the method or interactions of solvents
what does putting a control sample through the instrument tell us with all the blanks?
with all the blank’s responses, you are able to identify the control sample’s response out of the other three responses
four types of precision
instrument, intra-assay, interlaboratory, intermediate
instrument precision
a single scientist performs the same experiment with the same sample and the same instrument and takes multiple measurements
intra-assay precision
repeatability; the same scientist performs the same procedure on the same day using the same aliquot of the same starting sample using the same instrument multiple times
intermediate precision
ruggedness; different scientists in the same lab perform the same procedure using aliquots from the same sample on different days with different instruments
interlaboratory precision
reproducibility; aliquots of the same sample are sent to different labs to be analyzed by different scientists with different instruments on different days using the same procedure
how reproducible am I when performing the same experiment?
intra-assay precision
how reproducible is the experiment when performed with in our lab?
intermediate precision
how reproducible is the experiment when performed across different labs?
interlaboratory precision
how reproducible is the value that comes from an instrument?
instrument precision
most precise to least precise types of precision
Most Precise: instrument
intra-assay
intermediate
Least Precise: interlaboratory
before analyzing a red marker, a sample of the solvent without any dye is analyzed; the instrument response must be less than 0.10 AU
method/solvent blank
before analyzing a red marker from the production line, three separate solutions of standards of the expected dye concentration are analyzed by the spectrophotometer; the st. dev. of the instrument response must be less than 0.10 AU
using a control sample to measure precision
when analyzing each red marker, the instrument response for a single marker was measured three times; the st. dev. for the average instruction response must be less than 0.10 AU
precision
when analyzing the ten red markers each hour, the percent error for any single marker must not exceed 1%
accuracy
when purchasing a new instrument to perform these analyses, a series of standards of various known concentrations of the red dye are analyzed and the slope of the best fit line determined; the steeper the line, the better
sensitivity
what makes a reference source scholarly?
- published in a scientific journal, access freely or through a library?
- references cited throughout the text
- text should be peer-reviewed by other experts in the same area as what the text is focused on
