final exam Flashcards
what percentage of the normal population will fall between the +/- 2 SD and +/- 3SD range on a normal curve?
4.2 %
the standard deviation divided by the mean and multiplied by 100 gives you the ?
coefficient of variation
what are some steps you would take if you were running controls and they fell between +/- 2 SD and +/- 3 SD?
- repeat controls
- new control
- check reagents
- replace reagents
- calibrate analyzer
- call field service / let others know
what would you never do if your controls were falling between 2 SD and 3 SD?
run patient samples
define mode
most often repeated # in a set of data
how is the mean determined?
sum of all #’s divided by the number of numbers in the set
define median
value physically in the middle of a set of data
what is accuracy?
a measure of how close to the true or actual value a physical measurement is
what is precision?
consistency
what is the formula for standard deviation?
i can’t type that… look at notes
give the total % of a normal population that would be included in +/- 3 SD from the mean
99.7%
quality control gives you information on the ____ of your procedures and/or laboratory analyzers
reliability
what is mathematical formula for variance?
look at notes
a t-test is used to determine what?
if there is significant difference in the results obtained by 2 dif. methods for the same constituents
define degrees of freedom
n-1
what is a levy-jennings chart?
chart used to plot QC values and to determine SD 95% confidence limits
what information does a levy-jennings chart provide?
about how well the analyzers are performing over time
what is a shift?
4 or more consecutive plots on, above, or below the mean
what is a trend?
4 or more successive plots in the same direction ascending or descending
do laboratories determine their own normal ranges?
yes, may use reference ranges established by the manufacturer
how do laboratories go about establishing their own normal ranges?
20 points, apparently healthy patients
what is the purpose of a lab establishing its own normal range?
because to establish normal range for the area population
would a single data point that fell out of control be used to determine the statistics for the next month’s QC chart? explain
yes because of random error
generally speaking, random error is due to what?
human imprecision, chance occurrences without an identifiable cause
