If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, using the XXXXXXXXXXrule to approximate, what is the percentage of light bulbs...

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, using the 68-95-99.7 rule to approximate, what is the percentage of light bulbs having a life less than 1500?

The weights of fish in a lake are normally distributed with mean 20 lbs and standard deviation 6. If 4 fish are randomly selected, what is the likelihood that the mean weight will be between 17.6 and 23.6 lbs?

At one college, GPA’s are normally distributed with a mean of 3 and a standard deviation of 0.6. What is the 80th percentile?