9. Statistics Flashcards
Continuous
Continuous:
can take any value in a
given range
e.g. height or weight
Discrete:
Discrete:
can take an integer value only
e.g. visual analogue scale
Ratio:
Ratio:
a data series that has zero as its
baseline, such as heart rate and
temperature (degrees Kelvin)
Interval:
Interval:
a data series that has zero as a
point on a larger scale, such as
temperature (degrees Celsius)
Numerical data (obtained from measurements)
Continuous
Discrete:
Ratio:
Interval:
Categorical data (grouped data
Nominal (unordered)
Ordinal (ordered):
Nominal (unordered):
Nominal (unordered):
data comes from mutually exclusive
unranked groups, e.g. procedural outcome (success or
failure) and gender (male or female)
Ordinal (ordered):
Ordinal (ordered):
ranked groups, e.g. categorical pain
rating scale (mild, moderate and severe), ASA grade (class I,
II, III, IV, V)
Probability
Probability is the chance of occurrence of an event.
It has a value
between 0 and 1.
The probability density curves are used to describe the
distribution of data in the given population.
They can be of different types:
Types of distribution of data
normal (most important), binomial (value of 0 or 1) or Poisson
distribution.
Characteristics of a normal distribution:
also called the Gaussian distribution
describes the distribution of continuous variables
bell-shaped symmetrical curve
mean, median and mode are identical
tails do not touch the baseline
peaks if variance (standard deviation) is low
flattens if variance (standard deviation) is high.
Mean:
it is the sum of all the values, divided by the number of values.
Median
it is the point that has half the values above and half below.
Mode:
it is used when we need a label for the most frequently occurring event.
Standard deviation:
it indicates how much a set of values is spread
around the average. It is a measure of dispersion.
Standard error of the mean
: it is the standard deviation of the
sample-mean estimate of a population mean. It gives an idea of how
closely the estimated mean value (from the sample) is likely to
represent the true mean value (from the general population).
It is worth remembering that:
what are the % SD for 1 2 3
± 1 standard deviations includes 68.2% of the data
± 2 standard deviations includes 95.4% of the data
± 3 standard deviations includes 99.7% of the data.
Reliability
Reliability is the dependability of a test
(consistency and
reproducibility).
Precision
Precision is the extent to which random variability is absent from the
test.
Reliability of a test is dependent upon its precision.
Validity
Validity is the extent to which the test measures what it was designed
to measure.
It has two components: sensitivity and specificity.