Quality Control Statistics

Question 1

What is the definition of mean?

Answer 1

mathematical average

Question 2

What is the formula for the mean?

Answer 2

sum of all the data points divided by number of data points

Question 3

Calculate the mean of 3, 7, 7, 19.

Answer 3

= (3+7+7+19)/4
= 36/4
= 9

Question 4

Calculate the median of 3, 7, 7, 19.

Answer 4

= (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

Question 5

Calculate the mode of 3, 7, 7, 19.

Answer 5

mode is the most common observation, so the mode is 7

Question 6

What is the formula for determining percent sensitivity?

Answer 6

= # disease persons with a positive test result divided by total # Disease Persons multiplied by 100
= TP / (TP + FN)

Question 7

What is the formula for determining percent specificity?

Answer 7

= # nondiseased persons with a negative test result divided by total number of nondiseased persons multiplied by 100.
= TN / (TN + FP)

Question 8

What is the formula for determining positive predictive value (PPV)?

Answer 8

= TP / (TP + FP)

Question 9

What is the formula for determining negative predictive value (NPV)?

Answer 9

= TN / (TN + FN)

Question 10

What is the definition of specificity?

Answer 10

probability of correctly classifying a non-diseased person as non-diseased
true negative rate

Question 11

What is the definition of False Positive Rate?

Answer 11

probability of correctly classifying a non-diseased person as diseased

Question 12

What is the definition of sensitivity?

Answer 12

probability of correctly classifying a diseased person as diseased
true positive rate

Question 13

What is the formula for the False Positive Rate?

Answer 13

= FP / (TN + FP) x 100
or
= 1 - specificity

Question 14

What is the formula for the False Negative Rate?

Answer 14

= FN / (TP + FN) x 100
or
= 1 - sensitivity

Question 15

What is the formula for the total number of diseased persons?

Answer 15

TP + FN

Question 16

What is the formula for the total number of non-diseased persons?

Answer 16

TN + FP

Question 17

What is the definition of accuracy?

Answer 17

closeness of a measured value to its true value. In other words, the ability to get close to the bulls eye.

Question 18

What is the definition of reproducibility?

Answer 18

closeness of repeated measurements of the same quantity. in other words, the ability to hit the same spot on the target.

Question 19

With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- one standard deviation?

Answer 19

68%

Question 20

With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- two standard deviations?

Answer 20

95%

Question 21

With ‘normal distribution’, what is the value of observations that will make up the distribution between +/- three standard deviations?

Answer 21

99%

Question 22

What three conditions can be shown using a Levey-Jennings plot?

Answer 22

1. trend
2. shift
3. dispersion

Question 23

Describe a Levey-Jennings plot?

Answer 23

plot of control results on the y-axis versus time on the x-axis.

Question 24

What is dispersion?

Answer 24

increased frequency of both high and low numbers. the plot has values above and below the line designating 2SD.

Question 25

What is a trend?

Answer 25

progressive drift of reported values from a prior mean. the plot shows a drift consistently above or below the line designating 2SD.

Question 26

What is a shift?

Answer 26

an abrupt change from the established mean. The plot shows a very abrupt shift above or below the line designating 2SD.

Question 27

What is the number and type of patients that would be tested to establish a reference range?

Answer 27

100 patient from the local community.
Include variations in race, sex, age, weight, nutritional status, degree of physical activity, geography, time of day.
The range is established with the 95% confidence limits.

Question 28

When were the CLIA ‘88 regulations published?

Answer 28

2003