A new iTunes competitor is testing the speed of their website. Data from the website show that the length of time required to download a typical song has a Normal distribution with a mean of 93 seconds and a standard deviation of 12 seconds.

They measure a sample of 36 downloads. What is the probability that the mean download time is under 91 seconds?

The Woodcock Johnson Test of Cognitive Abilities gives scores that are approximately normally distributed with a mean of 100 and a standard deviation of 15. Consider the mean of a sample of 30 children. What is the threshold above which only 5% of samples of this size score?

Water with nitrate concentrations above 10 mg/L is toxic to infants. Scientists testing the water take 5 liters, and measure the mean amount of nitrate per liter.If groundwater near a dairy farm is Normally distributed with anaverage of 8 mg/ L with a standard deviation of 2 mg/ L, what is the probability that the mean is above the danger level? Copy paste your answer from Excel, or enter a number you have calculated that is accurate to at least three places past the decimal.