a student has to measure the distance from her observatory to a distant star . however due to atmospheric disturbance any measurement will not yield the exact distance as a result the student has decided to make a series of measurement and then use their average value to estimate of the actual distance if the student believe that the value of the successive measurement are independent random variable with mean of the distance light year and variance is 2 light year how many measurement need she make to be at least 99 percent?