Practice Test 4

A coach wants to estimate the average time it takes all members of the track team to run 400 meters. She takes three different random samples of 20 runners from the team on three different days. The sample means are 78.4 seconds, 80.1 seconds, and 79.0 seconds. About how much do these sample mean estimates vary (use the range)?

A science teacher wants to estimate the average mass of all the small rocks in a bucket (the population). She randomly selects 30 rocks and finds a sample mean mass of 42.6 grams. Then she takes another random sample of 30 rocks and finds a sample mean of 41.9 grams. Which conclusion is most reasonable?​