inferential stats Flashcards
what are inferential statistics?
they help us infer meaning from the data ie they help draw conclusions and make predictions
why does psychology use statistical tests?
to test the probability that an event occurs due to chance
what does p ≤ 0.05 mean?
means that there is a 5% chance that the results happened due to chance
it is the standard p value in psychology
what does p ≤ 0.01 mean?
there is a 1% chance that the results happened due to chance
you may decrease the p value for new medicine tests etc
what is a type 1 error?
if you accept your alternate hypothesis when you should have accepted the null it is a type 1 error
is a false positive
what is a type 2 error?
if you accept your null hypothesis when you should have accepted the alternate hypothesis it is a type 2 error
is a false negative
when do you use a chi-squared test?
when the data is nominal and it is an independent measures design
when do you use a mann-whitney U test?
when the data is ordinal or interval and the design is independent measures
when do you use a binomial sign test?
when the data is nominal and the design is repeated measures/matched pairs
when do you use Wilcoxon Signed Ranks test?
when the data is ordinal/interval and the design is Repeated Measures/ Matched Pairs
when do you use a Spearman’s Rho test?
when you have a correlation (with ordinal/interval data)
why would you use a parametric test?
if your data is normally distributed
when do you use a non-parametric test?
when your data is skewed
what is your observed value?
is the value from your data
what is a critical value?
found in a critical values table.
you can compare your observed value to this to see if your result is significant
in which stats tests does the observed/calculated value need to be less than the critical value to be significant?
binomial sign test
wilcoxon signed ranks
mann whitney u
in which stats tests does the observed value need to be more than the critical value to be significant?
chi squared
spearmans rho
what are the calculation steps for mann whitney u?
- rank scores (from lowest to highest)
- use formula to find U:
U1 = n1n2 + n1(n1+1)/2 – R1
U2 = n1n2 + n2(n2+1)/2 – R2
- calculate the smaller U
- if the calculated value U is less than the critical U value, reject null
- if calculated U value is higher than critical U value, accept null
what are the calculation steps for wilcoxon signed ranks test?
the difference in values of each condition is calculated, differences are then ranked.
the sum of the positive and negative values is found and T is the smallest of these values
if the calculated W is less than the critical value, reject null
if the calculated is higher than the critical, accept null
what are the calculation steps of chi-squared test?
(note: practice this don’t just rely on the flashcard for the love of god)
add totals for each column
calculate observed and expected frequencies (use formula):
χ2 = Σ(Oi − Ei)^2/Ei
chi value - adding all cells of expected frequencies
if the calculated Chi value is less than the critical Chi value, accept null
if the calculated Chi value is higher than critical Chi value, reject null
what are the calculation steps for binomial sign test?
determine positive and negative values for data
add each positive and negative assigned direction
smallest direction score = S value
if the calculated S value is less than critical value, reject null
if calculated is higher than critical value, accept null
what are the calculation steps for spearman’s Rho correlation?
rank each dataset INDIVIDUALLY
find DIFFERENCE between each dataset
SQUARE DIFFERENCE (d2) and find the TOTAL of (d2) column
use formula to find rho:
r = 1 - (6ΣD^2)/(n(n^2-1))
just search up the formula i got no clue how to write it out on these flashcards and im like 90% sure you don’t even need to memorise it
if the calculated Rho value is less than the critical value, accept null
if calculated is higher than critical, reject null
how to calculate the degrees of freedom?
(number of rows of data - 1) x (number of columns of data -1)
how do you calculate the expected value for chi squared test
(row total * column total) / overall total
how do you rank conditions for a mann whitney u test
rank conditions TOGETHER
how do u rank conditions for spearmans rho
INDIVIDUALLY
how is ranking involved in wilcoxon signed ranks
you have to rank the difference between the two conditions
