Quality Control Statistics Flashcards
What is the definition of mean?
mathematical average
What is the formula for the mean?
sum of all the data points divided by number of data points
Calculate the mean of 3, 7, 7, 19.
= (3+7+7+19)/4
= 36/4
= 9
Calculate the median of 3, 7, 7, 19.
= (7 + 7) / 2
= 7
in this example, because we have an even number of data points, we take the two in the middle and average
Calculate the mode of 3, 7, 7, 19.
mode is the most common observation, so the mode is 7
What is the formula for determining percent sensitivity?
= # disease persons with a positive test result divided by total # Disease Persons multiplied by 100
= TP / (TP + FN)
What is the formula for determining percent specificity?
= # nondiseased persons with a negative test result divided by total number of nondiseased persons multiplied by 100.
= TN / (TN + FP)
What is the formula for determining positive predictive value (PPV)?
= TP / (TP + FP)
What is the formula for determining negative predictive value (NPV)?
= TN / (TN + FN)
What is the definition of specificity?
probability of correctly classifying a non-diseased person as non-diseased
true negative rate
What is the definition of False Positive Rate?
probability of correctly classifying a non-diseased person as diseased
What is the definition of sensitivity?
probability of correctly classifying a diseased person as diseased
true positive rate
What is the formula for the False Positive Rate?
= FP / (TN + FP) x 100
or
= 1 - specificity
What is the formula for the False Negative Rate?
= FN / (TP + FN) x 100
or
= 1 - sensitivity
What is the formula for the total number of diseased persons?
TP + FN
What is the formula for the total number of non-diseased persons?
TN + FP
What is the definition of accuracy?
closeness of a measured value to its true value. In other words, the ability to get close to the bulls eye.
What is the definition of reproducibility?
closeness of repeated measurements of the same quantity. in other words, the ability to hit the same spot on the target.
With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- one standard deviation?
68%
With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- two standard deviations?
95%
With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- three standard deviations?
99%
What three conditions can be shown using a Levey-Jennings plot?
- trend
- shift
- dispersion
Describe a Levey-Jennings plot?
plot of control results on the y-axis versus time on the x-axis.
What is dispersion?
increased frequency of both high and low numbers. the plot has values above and below the line designating 2SD.
