the life span of a DVD player produced by one major company is known to be normally distributed with the mean of 6.2 years. If 4.

the life span of a DVD player produced by one major company is known to be normally distributed with the mean of 6.2 years. If 4.02% of these DVD players have a life span of more that 8 years, what is the standard deviation. PLease show me the fomula and how you got the answer