LECTURE 8 non para stats

Question 1

what are contasts

Answer 1

when want to further investigate a significant main effect found in an ANOVA

Question 2

what can you do to further investigate a main effect

Answer 2

multiple t test (type 1 error)
planned ( a priori) comparison contrast
unplanned (post hoc) comparison contrast
simple main effects

Question 3

what is a planned (a priori) contasts

Answer 3

do not require significant anova
carry out small no of specific comparisons that are driven by a hypothesis

variance caused by experiement due to subjects assigned to diff groups - can break down to test hyp about which groups differ

Question 4

what is an unplanned (post hoc) contrast

Answer 4

no planned hypothesis that requires significant anova to carry out several comparison simultaneously
designed to prevent type 1 error by keeping significant level at 0.5

Question 5

what is simple main effects comparison

Answer 5

in 2 ay anova test for effect of one factor at each level of the other factor

Question 6

rules when chosing contrasts

Answer 6

contrasts must be independent of eachother (test unique hyp)
only do two contrasts of variance at once
k-1 - 1 less contrast than no of goups

(THEREFORE if compare first two cond and not last, 1 = 1,, 2 = -1 and 3=0) - add to 0

Question 7

formula for planned comparison

Answer 7

C = C1M1 + C2M2…etc
C = weighting of coefficient - sum to 0
therfore test whether m1 sig diff from m2

Question 8

spss contrast : Deviation

Answer 8

each condition compared to overall mean except 1st and last category which is reference mean

Question 9

spss contrast: simple

Answer 9

mean of each condition contrasted with first or last cat

Question 10

spss contrast: helmert

Answer 10

mean of each cond except last compared with mean of subsequent cond

Question 11

spss contrast: repeated

Answer 11

mean of each cond compared to mean of next

Question 12

spss contrast: polynomial

Answer 12

means contrasted in terms of fitting to a trend ie linear, quadratic etc

Question 13

Post hoc test for repeated measures

Answer 13

bonferonni
divide significance level by number of tests
run t test
compare sig level in spss to new sig level
#’bonferonni correction’

Question 14

independent measures post hoc

Answer 14

bonferonni
tukey
dunnett
REGWQ

Question 15

describe tukey post hoc test

Answer 15

pairwise comparisons between condition means when no prior expectation of when differences equivalent to t tst - differences lie in SE
general error term from diff between mean (MSerror)

mean 1 sample - mean 2 sample / SQRT of MSerror/n