Question-Bank 1g – Tukey/Dunnett tests @UWE_KAR Practice & Communication of Science Question-Bank 1g – Tukey/Dunnett tests @UWE_KAR

So your ANOVA is sig: is that it? 1-way, 2-way/factorial ANOVA can deal with one (1-way) or two (2-way) factors and produces a single p-value for each factor eg Q1 from the anova.docx q-bank two factors (temp and inoculum dose) each has a p-value (0.071 and 0.000) so temp is non-sig and does is sig but dose has 4 levels! how do I apply this single p-value to the pattern of results within the levels? (called post hoc testing) One approach (great for exams!) is the Least Significant Difference but there are others…

Post Hoc Tests and ANOVA Least Significant Difference tells you how far apart any pair of means (ie two levels of a factor) need to be to be significant Tukey Similar to the LSD, the Tukey test can test all levels against each other levels to be compared with each other are identified and referred to as a ‘family’ for that ‘family’, you make the confidence level for the many individual comparisons stricter so overall ‘family’ level is 95% it’s automated in Minitab and not suited to calculation in an exam! 

Post Hoc Tests and ANOVA Dunnett test used where one level is obviously a ‘control’ or ‘reference’ level comparisons will then be made between this control and each of the other, ‘experimental’ levels the test creates CIs for differences between mean of each ‘expt’ group and mean of ‘control’ group if a CI contains 0, then no significant difference remember, 0 is the Null Hypo so if 0 is in the CI then it (the Null Hypo) is not unusual and can’t be rejected as before, multiple comparisons means that individual confidence levels are increased so overall ‘family’ confidence level is appropriate (95%) like Tukey, it’s automated in Minitab and not suited to calculation in an exam! 