21. A producer specifies that the mean lifetime of a certain type of battery is at least 240 hours. A sample of 18 such batteries yielded the following data.

237 242 232 242 248 230 244 243 254 262 234 220 225 236 232 218 228 240 Assuming that the life of the batteries is approximately normally distributed, do the data indicate that the specifications are not being met?