Given the following hypothesis: h1: 400 h0: 400 h1: 7 10 h0: 10 self-review 10–3 the mean life of a battery used in a digital clock is 305 days. the lives of the batteries follow the normal distribution. the battery was recently modified to last longer. a sample of 20 of the modified batteries had a mean life of 311 days with a standard deviation of 12 days. did the modification increase the mean life of the battery?