The article below points out common forms of statistical errors in the biomedical literature. I wanted to talked about this discipline rather than IS because everything I read about dietary or healthy food does not sound credible. For multivariate analyses, these are:
1. Not confirming that the data met the assumptions of ANOVA.
ANOVA assumes that the response variable is approximately normally distributed within each level of the explanatory variable and that the variability of these distributions is approximately the same. If data are not data are not normally distributed, than the data need to be mathematically transformed into distributions that are more normally distributed.In a way, this error also sound similar to a researcher using secondary data or existing statistics that are inappropriate for his or her research question, which was described in the previous chapter.
2. Not Identifying the Procedure Used to Adjust for Multiple Comparisons in ANOVA.
ANOVA is a group comparison that determines whether a statistically significant difference occurs somewhere among the groups studied. If a significant difference occurs, ANOVA is followed by a multiple comparison procedure that compares combinations of groups to determine which groups differ statistically.
3. Not Testing the Explanatory Variables for Interaction or Colinearity
Two explanatory variables are said to interact if the effect of one of the response variables depends on the level of the other. Interaction implies that the factors should be considered together, not separately. Two variables are said to be colinear if they are highly associated and therefore provide the same information in the model.
4. Not Indicating the Goodness-of-Fit of the Model to the Data
Goodness-of-fit indicates how well the model expresses the relationships observed in the data. In multiple regression analysis (not ANOVA), the value of R2 should be reported. This value indicates how much of the variation in the response variable is explained by the factors included in the model. Thus, the higher, the better.
Errors in interpreting differences between groups include:
1.Not Reporting Confidence Intervals with Estimates
When interpreting any difference, whether it is statistically significant or not, the direction and magnitude of the difference should be evaluated. However, because a study is based on a sample of the population of interest, rather than on a census of the population, its results are actually estimates of the differences expected if the study were to be repeated on the entire population. Thus, another factor that should be considered when evaluating differences is the precision of the estimate.
2. Reporting Only Relative Differences and Not Absolute Ones
The absolute difference between groups is simply the mathematical difference between their values, whereas the relative difference is the absolute difference expressed as apercentage. By themselves, relative differences can mislead because they can make differences appear to be larger or smaller than they really are.
3. Not Differentiating Between Unit of Observation and the Number of Patients Improved
The unit of observation or the unit of analysis is what is being studied. In clinical research, the unit of observation is usually the patient. However, sometimes the unit issomething other than the patient. The problem comes when, say, differences are reported for the unit of observation but not for the number of patients in whom differences occurred. For example, if a drug markedly improves mean glomerular filtration rate in patients with renal disease, it may also be helpful to know how many patients actually improved.
Reference
Lang Tom. Common statistical errors you can find. Errors in multivariable analyses and in interpreting differences between groups. AMWA Journal, Vol 18, No 3. 2003
http://www.aliquote.org/cours/2006_cogmaster_A4/ressources/Statistical_Errors_Part2.pdf