An environmental protection agency wishes to investigate the effectiveness of the 'Environment awareness' weekend courses which it ran for the general public. In order to gauge the effectiveness of the weekend course in improving the participants' knowledge of environmental issues, participants are asked to fill in a long questionnaire before attending the course and then fill in the same questionnaire after attending the course. The maximum score on the questionnaire was 1000. The results for a sample of 20 participants are given below:
Use a Wilcoxon test to find if there is any evidence that participants' knowledge of environmental issues is increased by attending the course. (N.B. Use the Normal approximation.)