Background

You will be providing support to the retail company's manager in charge of logistics. The retail company would like to run a test of the new trucking company. They are willing to devote 100 trips by truck from a distribution center to a store for the test. For each of the 100 trips, you can choose which trucking company will perform the delivery.

Question

Without any statistical analysis, what would you consider a sizable drop in the proportion of on-time deliveries? Select a minimal effect size that would be persuasive for the company.