a sample data has mean x_bar = 30 and variance s=144 find an interval that contains at least 15/16 of the observation in this sample?
mean = 30
sd = √144 = 12
15/16 = .9375
go to
http://davidmlane.com/normal.html
click on "value from an area"
enter: .9375 for area, 30 for mean, 12 for SD
click on "between" and read the two boundaries