Labroatory Statistics

Question 1

What is a reference range used for?

Answer 1

To identify abnormal results by comparing a patient’s value of the variable of interest to a reference range

Question 2

What is a 95% reference range?

Answer 2

Is constructed with the aim of including 95% of the results that would be obtained from a group of healthy individuals

Question 3

How many methods can be used to construct a reference range when using a large random sample of results from healthy individuals?

Answer 3

Two
Method 1
Method 2

Question 4

When is method one used?

Answer 4

Suitable for when results follow a normal distribution.
Percentage points from the normal distribution provide the limits:
95% = 1.96 multiplier
90% = 1.64 multiplier

Question 5

When is method two used?

Answer 5

If the random sample is not from a normal distribution then sample percentiles can be used to provide limits:
95% = 2.5th and 97.5th percentiles
90% = 5th and 95th percentiles

Question 6

When is method one useful?

Answer 6

With as large a sample size as possible, the sample size should be at least 200 observations when normality is observed

Question 7

When is method two useful?

Answer 7

If large samples we’ll in excess of 200 observations are available

Question 8

What is measurement error?

Answer 8

Several measurements of property on an individual or sample of material may not always give the same result because of variation in the measurement process

Question 9

What is the within-individual standard deviation?

Answer 9

The common standard deviation of repeated measurements

Question 10

How do you measure the size of the measurement error?

Answer 10

By taking the standard deviation of repeated measurements of the same individual

Question 11

What are method comparison studies?

Answer 11

Are used to investigate the agreement between two methods of measuring the same property