RESEARCH METHOD COHEN ok

MEASURES OF DIFFERENCE BETWEEN GROUPS AND MEANS 549
Box 24.45
The Tukey test
Multiple comparisons
Dependent variable: Standardized mathematicsscores(percentages)
Tukey HSD
Chapter 24
95 % confidence interval
Mean
(I) Grouping of school (J) Grouping of school difference (I–J) SE Sig. Lower bound Upper bound
Rural primary Rural secondary −0.59 2.563 0.996 −7.19 6.01
Urban primary 9.21* 2.541 0.002 2.67 15.76
Urban secondary 8.15* 2.366 0.003 2.06 14.24
Rural secondary Rural primary 0.59 2.563 0.996 −6.01 7.19
Urban primary 9.80* 2.531 0.001 3.28 16.32
Urban secondary 8.74* 2.355 0.001 2.67 14.81
Urban primary Rural primary −9.21* 2.541 0.002 −15.76 −2.67
Rural secondary −9.80* 2.531 0.001 −16.32 −3.28
Urban secondary −1.06 2.331 0.968 −7.07 4.94
Urban secondary Rural primary −8.15* 2.366 0.003 −14.24 −2.06
Rural secondary −8.74* 2.355 0.001 −14.81 −2.67
Urban primary 1.06 2.331 0.968 −4.94 7.07
*. The mean difference is significant at the 0.05 level.
analysis is continued for the urban primary and
the urban secondary school. One can see that the
two types of rural school do not differ statistically
significantly from each other, that the two types of
urban school do not differ statistically significantly
from each other, but that the rural and urban
schools do differ statistically significantly from
each other. We can see where the null hypothesis
is supported and where it is not supported.
In fact the Tukey test in SPSS presents this very
clearly (Box 24.46).
Here one group of similar means (i.e. those not
statistically significantly different from each other:
the urban primary and urban secondary) is placed
together (the column labelled ‘1’) and the other
group of similar means (i.e. those not statistically
significantly different from each other: the rural
primary and rural secondary) is placed together
(the column labelled ‘2’). SPSS automatically
groups these and places them in ascending order
(the group with the lowest means appears in the
first column, and the group with the highest means
is in the second column). So, one can see clearly
Box 24.46
Homogeneous groupings in the Tukey test
Standardized mathematics scores (percentages)
Tukey HSD a,b Subset for alpha = 0.05
Grouping of school N 1 2
Urban primary 141 50.64
Urban secondary 194 51.70
Rural primary 134 59.85
Rural secondary 136 60.44
Sig. 0.973 0.995
Means for groups in homogeneous subsets are displayed.
a. Uses Harmonic Mean Sample Size = 147.806.
b. The group sizes are unequal. The harmonic mean
of the group sizes is used. Type I error levels are not
guaranteed.
that the difference between the school lies not
in the fact that some are primary and some are
secondary, but that some are rural and some are