Find the mean and standard deviation for uniform

The mean is found by the formula:                      (a + b) / 2  

The standard deviation is found by the formula:  sqrt[ (a - b)²  12 ]

 

For  U(4, 13):     a = 4     b = 13

 

--->   mean  =  (4 + 13) / 2  =  17/2  =  8.5

 

--->  standard deviation  =  sqrt[ (13 - 4)² / 12 ]  =  sqrt[ 81 / 12 ]  =  2.598