Inferential Statistics Flashcards
What do inferential statistics do?
they make inferences (conclusions) about the population
what are the 2 types of inferential statistics?
Frequentist (uses sample data to draw conclusions by empathising frequency / probability)
Bayes
What are the 4 features of frequentist inferential statistics?
Null hypothesis significance testing
P-values
Effect size
confidence intervals
What is Null hypothesis significance testing (NHST)?
when an experimental factor is tested against a hypothesis of no effect or relationship
Null Hypothesis is H_?
H0
no difference
Alternative Hypothesis is H_?
H1
difference
has 2 types
what are the 2 types of Alternative (experimental) hypothesis?
Directional (one tailed)
Non-directional (two tailed)
What is the P-value rule?
if p-value is below 0.05 then result is ‘statistically significant’
the level we accept results is also known as ‘alpha level’
can use 1% to be stricter
How do P-values work in frequentist inferential statistics?
probability result found occurred by chance assuming null hypothesis is true
tells us if there’s false-positives
what does it mean if the p-value is high?
more likely results are ‘statistically non-significant’
How do you write up a p-value that’s written as e-16 (for example)?
means p-value is really small
p<.001
What are Effect Sizes?
tell us about the magnitude of the difference or similarity of a correlation
What is the most popular effect size?
Cohen’s d (measures size of difference between groups)
Pearsons r (measures strength of relationship between 2 variables)
When is cohen’s d often used?
often used in independent samples t-tests
continues data with large samples
Chi Square
used to discover if there is a relationship between 2 categorical (nominal) or sometimes ordinal variables
What can Chi Square only be used for?
only be used for a between subjects design
groups must be independent
what is the symbol for Chi Square
χ2
symbol comprised of small greek letter chi and 2 superscript
How to calculate expected frequencies
Row total x column total divided by total N
N = no. of ppts
Values taken from observed frequencies table
What does Chi square measure?
the difference between observed frequencies and expected frequencies
if they differ then suggested there’s an association between IV and DV
What is it called when Chi Square table has 2 rows and 2 columns?
Chi square that’s conducted will be known as 2x2 chi square
what is the goodness of fit test?
statistical hypothesis used to see how closely observed data mirrors expected data
