Statistics Flashcards
What assumptions are required for parametric tests to be valid?
Observations are independent.
Observations are drawn from a normally distributed population.
Different groups must have equal variance.
Data must be at an interval scale at least.
What are the two most common issues with experimental data that prevent the use of parametric tests?
Not knowing the underlying distribution of the data.
Data not being in the interval scale.
What assumptions are required to carry out non-parametric tests?
Observations are independent.
Sometimes: data are drawn from a continuous underlying distribution.
Main benefits of non-parametric tests?
Smaller sample size required.
Can use more forms of data.
Less impact from outliers.
What is the main downside of non-parametric tests?
Tests have less power
What does it mean when a test has less power?
Harder to reject the null hypothesis when it is false
What are the four scales of data?
Nominal
Ordinal
Interval
Ratio
Characterise nominal data
Data is categorised, no order
Characterise ordinal data
Data is categorised and ordered
Characterise interval data
Numerical differences between numbers has some meaning
Characterise ratio data
Scale has a natural zero point at origin
What are the two one-sample parametric tests?
Binomial and chi-squared
When can you use the binomial test?
When population consists of only two classes
What scale of data is required at least for the binomial test?
Nominal scale
When to use the chi-squared test?
When population consists of at least two classes
What is the minimum scale of data required for the chi-squared test?
Nominal scale
What are the three two-sample non-parametric tests?
Fisher exact test
Mann-Whitney U test
Wilcoxon test