Statistics from a country for four consecutive years show that car accidents are 4% higher at other times of daylight saving time than those at other times. These statistics show that the change of time has seriously affected the attention of drivers in a country. What are the prerequisites for reaching this conclusion? ['Drivers in this country have the same driving habits as drivers in other countries.', 'The observed increase in accident rates is almost always due to an increase in the number of minor accidents.', 'Research on the incidence of traffic accidents requires at least five years of observation.', 'No other factors such as school holidays and holidays that lead to increased accidents.']