Chapter 8 Flashcards
measurement of a single characteristic can vary.
variable
can result in many factors including genes, nutrition, environmental exposures, age, sex, and race.
biological differences
often account for the variations observed in medical data and include factors such as time of the day, ambient temperature or noise, and the presence of fatigue.
Ex Blood pressure is higher with anxiety or following exercise and lower after sleep.
different conditions of measurement
can produce different results.
Ex. A blood pressure measurement derived from the use of an intraarterial catheter may differ from a measurement derived from the use of an arm cuff.
different techniques of measurement
can also cause variation
Ex. Two different blood pressure cuffs of the same size may give different measurements.
measurement errors
types of variation can distort data systematically in one direction
Ex. Measuring and weighing patients while wearing shoes
systematic error
Inevitable inaccuracies in obtaining measurement.
random error
continuous measurement scale
quantitative characteristics
described by its features, generally in words
qualitative characteristics
Naming or categoric variables that are not based on measurement scales or rank order
nominal variables
Variables with only two levels
Dichotomous (binary) Variables
Data can be characterized in terms of the three or more qualitative values that have clearly implied direction from better to worse.
ordinal (ranked) variables
Data that is measured in continuous (dimensional) measurement scales.
Continuous (dimensional) variables
If a continuous scale has a true 0 point, the variables derived from it, it is where zero has a value
ratio variables
variables created by the ratio, and can be analyzed using the statistical method
risks and proportions as variables
