Given the task definition, example input & output, solve the new input case.
In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.
Example: Article: Homework can put you in a badmood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Answer: whether mood affects their learning ability
Output: Researchers did experiments on kids in order to find out _ .
It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment.

New input case for you: Article: Long after the 1998 World Cup was won, disappointed fans were still cursing the disputed refereeing decisions that denied victory to their team. A researcher was appointed to study the performance of some top referees. The researcher organized an experimental tournament involving four youth teams. Each match lasted an hour, divided into three periods of 20 minutes during which different referees were in charge. Observers noted down the referees' errors, of which there were 61 over the tournament. Converted to a standard match of 90 minutes, each referee made almost 23 mistakes, a remarkably high number. The researcher then studied the videotapes to analyse the matches in detail. Surprisingly, he found that errors were more likely when the referees were close to the incident. When the officials got it right, they were, on average, 17 meters away from the action. The average distance in the case of errors was 12 meters. The research shows the optimum distance is about 20 meters. There also seemed to be an optimum speed. Correct decisions came when the referees were moving at a speed of about 2 meters per second. The average speed for errors was 4 meters per second. If FIFA, football's international ruling body, wants to improve the standard of refereeing at the next World Cup, it should encourage referees to keep their eyes on the action from a distance, rather than rushing to keep up with the ball, the researcher argues. He also says that FIFA's insistence that referees should retire at age 45 may be misguided. If keeping up with the action is not so important, their physical condition is less critical.
Answer: analyse the causes of errors made by football referees
Output:
The experiment conducted by the researcher was meant to _ .