final exam

Question 1

what percentage of the normal population will fall between the +/- 2 SD and +/- 3SD range on a normal curve?

Answer 1

4.2 %

Question 2

the standard deviation divided by the mean and multiplied by 100 gives you the ?

Answer 2

coefficient of variation

Question 3

what are some steps you would take if you were running controls and they fell between +/- 2 SD and +/- 3 SD?

Answer 3

• repeat controls
• new control
• check reagents
• replace reagents
• calibrate analyzer
• call field service / let others know

Question 4

what would you never do if your controls were falling between 2 SD and 3 SD?

Answer 4

run patient samples

Question 5

define mode

Answer 5

most often repeated # in a set of data

Question 6

how is the mean determined?

Answer 6

sum of all #’s divided by the number of numbers in the set

Question 7

define median

Answer 7

value physically in the middle of a set of data

Question 8

what is accuracy?

Answer 8

a measure of how close to the true or actual value a physical measurement is

Question 9

what is precision?

Answer 9

consistency

Question 10

what is the formula for standard deviation?

Answer 10

i can’t type that… look at notes

Question 11

give the total % of a normal population that would be included in +/- 3 SD from the mean

Answer 11

99.7%

Question 12

quality control gives you information on the ____ of your procedures and/or laboratory analyzers

Answer 12

reliability

Question 13

what is mathematical formula for variance?

Answer 13

look at notes

Question 14

a t-test is used to determine what?

Answer 14

if there is significant difference in the results obtained by 2 dif. methods for the same constituents

Question 15

define degrees of freedom

Answer 15

n-1

Question 16

what is a levy-jennings chart?

Answer 16

chart used to plot QC values and to determine SD 95% confidence limits

Question 17

what information does a levy-jennings chart provide?

Answer 17

about how well the analyzers are performing over time

Question 18

what is a shift?

Answer 18

4 or more consecutive plots on, above, or below the mean

Question 19

what is a trend?

Answer 19

4 or more successive plots in the same direction ascending or descending

Question 20

do laboratories determine their own normal ranges?

Answer 20

yes, may use reference ranges established by the manufacturer

Question 21

how do laboratories go about establishing their own normal ranges?

Answer 21

20 points, apparently healthy patients

Question 22

what is the purpose of a lab establishing its own normal range?

Answer 22

because to establish normal range for the area population

Question 23

would a single data point that fell out of control be used to determine the statistics for the next month’s QC chart? explain

Answer 23

yes because of random error

Question 24

generally speaking, random error is due to what?

Answer 24

human imprecision, chance occurrences without an identifiable cause