Complex sentence: In their 1933 paper, Jerzy Neyman and Egon Pearson recommended that the significance level (e.g.0.05), which they called α, be set ahead of time, prior to any data collection.
Split into simpler sentences: In their 1933 paper, Jerzy Neyman and Egon Pearson called this cutoff the "significance level", which they named α. They recommended that α be set ahead of time, prior to any data collection.