Proceedings of MatricesFor IITTEP – ICoMaNSEd 2015
ISBN: 978-602-74204-0-3
Keynote Invited Papers Page 12
is an article mentioned using the Mann-Whitney U test for examining the different of the test result of two groups, but the data presented in the factorial design 2x2x2. The incorrectness
also happened when in the Method of Analysis section the statistics used is one way multivariate analysis of variance but in the results indicated the use of F-test to compare the
different of the mean of two groups in test of three independent variables. In another case, there is a study stated in the method of analysis section the multiple linear regression to
analyze the data in the level of α = 5 but in the result using the simple coefficient of correlation analysis for three independent variables with one dependent variable X1 with Y,
X2 with Y and X3 with Y. There is also a study that stated in the discussion and result section the regression analysis but the result is coefficient of correlation without the
regression equation.
2.9. Paired t-test and Unpaired t-test
There are still many articles that misused the paired and unpaired t-test. The paired t-test is used if the design using pretest and posttest or in two groups of different observational unit
but somewhat can be matched. The unpaired t-test is used when the design in the form of comparing two different groups or treatments. In one article that used pretest-posttest with
control group, the researcher tested on one group for one variable by using unpaired t-test.
This can be seen in the article that contain “the degree of freedom = n1 + n2 - 2. This can lead to wrong conclusion since for t 0,05; 14 = 2,145, but for t 0,05.28 = 2,043. What if
tcalculated = 2,100?
2.10. Factorial Design
The following are examples of the submitted articles with statistical methodology flaws:
In one article, the researcher used factorial design 2x2 and without to mention the significant of the effect of interaction heshe directly test the inter-cell different. A
mistake in test of the simple effect is comparing cells of different column and different row, i.e. a1b2 vs a2b1 and a1b1 vs a2b2. The correct way is to test only the
simple effect of the factor A in the level b1 a1b1 vs a2b1 and in the level of b2 a1b2 vs a2b2 and the factor B in the level of a1 a1b1 vs a1b2 and in the level of
a2 a2b1 vs a2b2.
In other study with factorial design 2x2x2 stated the main effect of all significant
factors and the existence of the effect of interaction between the two significant factors and among the three significant factors in its analysis of variance table. The
proper way is in the interaction whether it for two factors or for three factors, not necessary to do further test the test only for the simple effect.
In an experimental research with factorial design it is a mandatory to discuss the interaction effect in simple effect analysis. So it is unnecessary to discuss the main effect. The discussion
of the main effect will be useful if the interaction is not significant.
2.11. Using F-table and Result of Significant Value
