Project is graded on a scale of 1 to 5. if the random variable, x, is the project grade, what is the mean of the probability distributi

The set given by the project grade is {1, 2, 3, 4, 5}. If the random variable, X, is the project grade, the mean of the probability distribution is determined by:

Sum = 1 + 2 + 3 + 4 +5 
        = 15
Mean of the probability distribution is 15/n, where n = 5
        = 15/ 5
        = 3