Exercise 3

A group of students randomly selected 40 people and measured the accuracy of their wristwatches, with positive errors representing watches that are ahead of the correct time and negative errors representing below the correct time. The students reported a sample mean of + 1 min. and 57 sec and a standard deviation of 3 min. and 5 sec. Using a 5% significance level, what can be concluded about the accuracy of the average person's wristwatch?