Sixty children (20 each in three age groups) participate in an experiment to measure visual memory. Each child is given five tasks, of varied difficulty. The researchers are interested in whether the...

Sixty children (20 each in three age groups) participate in an experiment to measure visual memory. Each child is given five tasks, of varied difficulty. The researchers are interested in whether the impact of task difficulty differs by age Riggs et al. (2006).

Twenty-eight children in second grade each are given word-training in every combination of two different contexts and four different levels of repetition. The researchers are interested in whether the level of repetition, averaged over the two contexts, impacts the number of words learned Martin-Chang et al. (2007).