Fang Zhouzi, who is famous for battling against what he sees as pseudoscience and academic misconduct, posted a letter he received on his Weibo account which claimed  that fraud existed within the online ticket booking system launched by the Ministry of Railways. The person who wrote the letter says he has conducted  many tests using  the online ticket booking system, but each time has failed to book a  lower sleeper, which is often favored by passengers but more expensive than the upper or middle sleepers. He raised doubts that some lower sleepers are reserved for  special people and the tickets online are not randomly chosen.

@空杯子一个: Each time I bought tickets online they were upper lowers. After many attempts, the results still turned out to be upper sleepers. If I'm not absolutely "lucky", then all the tickets sold online are for upper sleepers.

@锦衣袂: Although most of the tickets I booked through the online ticket system were upper sleepers, I was also able to successfully book lower sleeper tickets.

@__lalla: If only I could be able to choose upper, middle or lower sleepers myself. Some people want the upper sleepers to save  money and the elderly, children, or pregnant women  choose lower sleeper tickets.

@CRH380A-6065L:  Don't reach a conclusion without investigating  and experimenting. It's not scientific. According to my experience, sometimes I  can book an upper sleeper ticket and sometimes I can  book a lower sleeper ticket. And on some occasions  the three tickets I booked were all lower sleepers. It proves that the online ticket booking system is random. Many lower and middle sleepers are booked by some people through phones and ticket windows, and naturally the remaining tickets are upper sleepers.