A random forest is an ensemble learning method that attempts to decrease the bias of decision trees. An infinite depth binary point is mislabeled decision tree can always achieve 100% training accuracy, provided that no outliers are present. K-Means clustering looks to find low-dimensional representation of the observations that explain a good fraction of the variance. Linear SVMs, widening the margin increases the number of observations that violate the margin of the classifier. A natural spline is a regression spline with the additional constraints that the function is required to be linear at the boundaries.