The mean arrival rate of flights at O'Hare Airport in marginal weather is 195 flights per hour with a historical standard deviation of 13 flights. To increase arrivals, a new air traffic control procedure is implemented. In the next 30 days of marginal weather, the mean arrival rate is 200 flights per hour.

210 215 200 189 200 213 202 181 197 199

193 209 215 192 179 196 225 199 196 210

199 188 174 176 202 195 195 208 222 221

Calculate the test statistic.(round your answer to 2 decimal places.)

Test statistic ?