Question: After a particular wet night, 12 worms surfaced on the lawn. Their lengths, measured in cm, were: 9.5, 9.5, 11.2, 10.6, 9.9, 11.1, 10.9, 9.8, 10.1, 10.2, 10.9, 11.0

Assuming that this sample came from a normal population with variance 4, calculate and interpret a 95% confidence interval for the mean length of all the worms in the garden.