The average weight of a medium size egg is found to be 3.2 oz, with a standard deviation of 0.13 oz. What is the heaviest egg (to 2 decimal places) that we are 95% confident is still medium size? 3.2 oz 3.33 oz 3.45 oz 3.46 oz

3.2 + 2 (0.13) = 3.46

95% of medium sized eggs lie within 2 standard deviations of the mean either side.

So, you just have to add 2 standard deviations to the mean; this will give the greatest possible weight you can expect 95% of medium sized eggs to have.