Question 3 A group of online MBA students was interested in comparing the operating time of cordless toothbrushes manufactured by two different companies, Oral B and Philips. Group members took a random sample of 18 toothbrushes from Oral B and 15 from Philips. Each was charged overnight, and the students recorded the number of hours of use before needing to be recharged. Oral B toothbrushes operated for an average of 129.7 hours with a standard deviation of 1.74 hours; Philip's toothbrushes operated for an average of 130.6 hours with a standard deviation of 1.72 hours. What is the value of the t-statistic for the difference in mean operation time for the null hypothesis