In a geology course, students are learning to use a balance scale to accurately weigh rocks. one student plans to weigh a rock 20 times and then calculate the average of the 20 measurements to estimate her rock's true weight. a second student plans to weigh a rock 5 times and calculate the average of the 5 measurements to estimate his rock's true weight. let’s say that the student who collected 20 weight measurements came up with a mean weight of 27.1 g with a standard deviation of 2.3 grams. the critical t-value for a 95% (one-sample) confidence interval with df = 19 is 2.09. which of the following is the resulting 95% confidence interval?