Final answer:
The mean number of daily oil changes is 39.1. The median number of daily oil changes is 39.5.
Step-by-step explanation:
a. Mean:
To find the mean, sum all the given numbers and divide by the total count: (31+56+29+39+23+43+27+17+33+40+29+62+40+48+46+20+26+49+43+46)/20 = 39.1
b. Median:
To find the median, first arrange the numbers in ascending order: 17, 20, 23, 26, 27, 29, 29, 31, 33, 39, 40, 40, 43, 43, 46, 46, 48, 49, 56, 62. The median is the middle value, which in this case is the average of the two middle values: (39 + 40)/2 = 39.5