A fleet of electric vehicles are to be investigated for the mileage performance per charge. Four vehicles have been chosen randomly from the fleet and four observations of miles were made for each vehicle. The data obtained from the experiment are below. What type of experimental design is this? What is the model and associated hypothesis?

vehicle	obs. 1	obs. 2	obs. 3	obs 4.	charging time
1	98	97	95	93	25
2	91	90	92	93	20
3	96	96	97	95	23
4	90	94	99	97	30