A hotel chain wants to know whether guests who book through…

A hоtel chаin wаnts tо knоw whether guests who book through third-pаrty websites spend less money on extra services (e.g., room service, spa) than those who book directly. The company collects data from a random sample of 75 third-party bookings and 60 direct bookings. The sample mean for third-party customers is $67, while the sample mean for direct customers is $42.   Based on this, the company concludes that direct-booking customers spend $25 more on extra services and will continue to do so in the future.   What is the most serious issue with this conclusion?