he average life of a battery is supposed to be 250 hours of continuous operation. A

random sample of 25 batteries is subject to discharge and the lifetime is recorded. The data is as follows

(in hours):

214, 289, 263, 291, 240, 207, 277, 252, 285, 287, 250, 297, 268, 286, 211, 232, 282, 216, 223, 234, 219,

280, 239, 249, 230

Using the sign test to test whether there is statistical evidence to conclude that the life of the battery is

less than 250 hours,

calculate the test statistic

.