Lecture 4 - Is This Test Result Normal? Flashcards
Clinical measurements yield 3 kinds of data. What are they?
- Nominal
- Ordinal
- Interval
What is nominal data?
Categorical with NO inherent order
eg: blood groups O, A, B, AB
eg: dead/alive, male/female (dichotomous)
What is ordinal data?
Inherent ordering but size of intervals between categories NOT specific
What is interval data?
Inherent ordering and interval between successive values is equal
What are two types of interval data?
- Continuous (weight, blood glucose)
2. Discrete (number of pregnancies)
Define mode
The most commonly observed value
Define median
The middle observation (50th centile)
Define mean
The average value, or sum of all values divided by total no. of observations
What does standard deviation measure?
Average distances that observations are located from the mean, derived from variance
What is the distribution of +/- 1 SDs?
68.2%
What is the distribution of +/- 2 SDs?
95.45%
How many standard deviations are in the normal range?
2
What is “normal range” most commonly defined as?
95% of non-diseased
Define validity
The degree to which the data measure what they were intended to measure (aka accuracy)
eg. calibration of lab instruments might ensure valid measurements
Define reliability
the extent to which repeated measurements get similar results (aka reproducibility and precision)
eg. repeated measurements of BP on different observers are ways to assess reliability
