Inferential Statistics 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 change
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)
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 dies 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)
-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:
-if the calculated Rho value is less than the critical value, accept null
-if calculated is higher than critical, reject null
