Statistics Flashcards
Validity
extent to which something measures what it claims to measure.
Internal Validity
Confidence that we can place in the cause and effect relationship in a study.
Ie something else did not cause the change
Reliability
extent to which an experiment, test, or any measuring procedure yields the same result on repeated trials.
External validity
The degree to which the conclusions in a study would hold for other persons in other places and at other times, i.e. its ability to generalise.
Standard Deviations
How spread out is the data from the mean
1: 68.2
2: 95.8
3: 99.7
How can you read skewed data?
IQ ranges
Median
Box and whisker plots
Used for skewed data
IQ ranges and median
Box and whisker plots
Mann Whitney U test
Non parametric
compares ordinal, interval, or ratio scales of unpaired data
Wilcoxon test
Before and after test on same population
Student t test
normally distributed
paired data – from the same group of patients
unpaired - different groups
Pearsons, Spearmans
Pearsons - norm dis
Spearmans - not
Correalation
Chi squared
non parametric
between 2 groups
compares percentages/ proportions
Type 1 error
the null hypothesis is rejected when it is true
T2 Error
the acceptance of the null hypothesis when it is actually false
Power of a study
the probability of (correctly) rejecting the null hypothesis when it is false, i.e. the probability of detecting a statistically significant difference
power = 1 - the probability of a type II error
Hawthorne Effect
People change their behaviour because they know theyre being studied
Parametric data
Normally distributed
Parametric test examples
Students T test
Pearsons
Likelihood ratio (positive)
Sens/ 1- spec
Likelihood ratio (negative)
1-sens/ spec
Absolute risk
CER - EER
Relative risk
EER/ CER
Relative risk reduction
Absolute risk/ CER
