A community psychologist is interested in whether signs containing encouraging messages or warning messages are more effective in increasing the vaccination rate in inner-city clinics. He chooses 2 clinics with similar numbers of child patients of similar ages. He posts encouraging-type signs in one clinic and warning-type signs in another and records the number of vaccinations per week over a period of 10 weeks. Is there a significant difference between the groups based on the type of sign?

Encouraging Signs	12 9 7 18 11 14 20 5 6 14
Warning Signs	9 8 11 12 19 20 12 3 5 8