Assignment:
Take lt Easy produces special shoes for runners, whose average life is 1250 km. In order to improve the product, they experiment with a new design, and test prototypes with a sample of 30 runners. The sample mean of product life is 1315 km, with a standard deviation of 70 km. Can we say that TakeltEasy has actually improved their product?
Provide complete and step by step solution for the question and show calculations and use formulas.