God didn't come down and hand us data, and Mother Nature has not taken her data and input it into a balanced data set for our convenience.
The 2 randomized blocks design used in each year constituted a balanced data set with a sufficiently high number of individuals (109 RILS in common) to allow a statistical estimate of GxE compared with some of the other sites.
As we do not want to a priori prefer flow to background or vice versa, we use the same amount of training data for the background and the flow in order to have a balanced data set for the SVM, which is a binary classification problem.
Consequently, to achieve a balanced data set in terms of gender, approximately 20% of the women were sampled randomly from the original data set.
Second, data mining methods were applied to a balanced data set in Delen et al. [ 8], whereas other studies, except Liu et al. [ 11], did not deal with imbalanced data which affected the performance of those methods.
It is quite a balanced data set: of the 6471 entries surviving curation, 2983 (46%) were categorized as "positives" based on their having been classified as "active" in the original publication.
In contrast, our proposed algorithm can constitute a nonparametric statistical analysis and provide a model-free and high-order-way measurement for epistasis without the limitation of a balanced data set.
Also, after quality control, some of our samples were removed from the data set, giving us an unbalanced data set; a balanced data set would give us the same overlap using the first and third approach.
Comparison of the number of sequences, sequence length, or GC content revealed no significant differences by oral condition or gender, indicating a balanced data set.
