DESCRIPTIVE DATA Flashcards
What is kurtosis
describes the peakedness of a distribution, how clustered the scores are around the mean
what is skew
the symmetry of the tails of the distribution
assuming normality looks like…
the distribution is unimodal
has moderate peakedness
ha symmetric tails
what does the mean tell us
the centre of the data
M= ΣX/n
provides an estimated level of performance in each condition
what does the sum of squared deviation (sum of squares) tell us
tells us about the total variability in the data set
SS= Σ (X-M)^2
tells us how reliable that estimated level of performance is (the mean)
what does standard deviation tell us
tells us average amount of variability around the mean
σ= √SS/n-1
or
σ= √Σ (X-M)^2/n-1
what are degrees of freedom
the number of values in the final calculation of a statistic that are free to vary
df = number of observations
what does the Z score tell you
how many SD the score is away from the mean
what is the Standard Error of the mean
an estimated variance of a distribution of sample means
SM = σ/√n
SM is the sample SD divided by the square root of the number of observations
what is a t distribution
a means to determine whether the difference is significant enough to say its not due to error or chance
when can a t test be used
when comparing 2 conditions only
can be use in a between subject or within subject design
Describe the F ratio
F is the statistic used to compare multiple group means
F = BG variance/WG Variance
BG - representing IV effect
WG - representing sampling error
foundation of an ANOVA
what is the null hypothesis
states that all groups are equal
the IV has no effect on the fc
what is the alternative (research) hypothesis
states that atleast one group mean is different
IV has an effect on DV
