find the mean, variance, and standard deviation for the number of cars sold at a dealership per day

Question

number of sales: 6     7     8     9

 

probability:       0.4    0.3  0.15    0.15

Answer 1

mean = weighted average = .4(6) + .3(7)+ .15(8) + .15(()= 2.4+ 2.1 + 1.2+ 1.35= 7.05

calculated very similar to a student's gpa

variance = sum of squared differences from the mean divided by n-1 where n= number of sales

standard deviation = sqrVar