Chiz-E-pizza, a family owned pizzeria, is famous not only for its innovative flavors, but also for delivering incredibly on time. However, during the last few weeks, the company has been facing an increase in customers complaints about late deliveries. Ernest Bell, the owner, suspects that the problem is related to the GPS platform they are currently using to calculate the estimated delivery time that is informed to customers. "This is affecting customer's expectations and compromising our level of service", he says. Shirley, his tech loving daughter, replies: "The platform is probably underestimating some important factors that impact on traffic. Let me investigate this".

Shirley wants to investigate what factors could be impacting the difference from the Estimated Time of Arrival - ETA from the current GPS platform to the actual delivery time. "It's been raining more than usual during the last month", she says, "I am convinced that it impacts traffic, and I guess the platform does not take this rain factor into account". Therefore, she takes precipitation reports from the last 30 days in order to analyze if rain is somehow related to the daily average delays.

The following table includes information about daily average delay and precipitation for the last 30 days.

Day Daily Average Delay (minutes) Precipitation (in) 1 15 0.76 1.5 0.07 12 0.51 16.5 0.06 5 1.5 0 6 0.27 10.5 0.29 8 17.5 0.24 9 19.5 1.1 10 12 0.31 11 13 10 12 28.5 1.06 13 1.5 0.03 14 22.5 0.7 15 1.5 0.01 16 13 0 17 1.5 0.04 18 30 1. 16 19 13.5 0.42 20 1.5 0 21 48 2.25 22 4.5 0.02 23 19 0 24 3 0.01 25 1.5 0.2626 1.5 27 1.5 28 1.5 0. 13 29 1.5 30 10.5 0.51