Imagine we were interested in the effect of supporters singing on the number of goals scored by soccer teams. We took 10 groups of supporters of 10 different soccer teams and asked them to attend three home games, one at which they were instructed to sing in support of their team (e.g., 'Fork 'em, Devils!'), one at which they were instructed to sing negative songs towards the opposition (e.g., 'You're getting sacked in the morning!') and one at which they were instructed to sit quietly. The order of chanting was counterbalanced across groups. An ANOVA with a simple contrasts using the last category as a reference was conducted. Looking at the output tables below, what does the first contrast (Level 1 vs. Level 3) compare?

A) No singing vs. negative singing

b) Positive singing vs. no singing

C)We cannot tell which groups the levels represent from this output.

D) Negative singing vs. positive singing

Within-Subjects Factors Measure: MEASURE_1 Dependent Singing Variable 1 Singing_Positi ve 2 Signing_negat ive 3 No_Singing Tests of Within-Subjects Contrasts Measure: MEASURE_1 Type Ill Sum Source Singing of Squares df Mean Square F Sig. Singing Level 1 vs. Level 3 19.600 19.600 7.230 .025 Level 2 vs. Level 3 6.400 6.400 6.000 .037 Error(Singing) Level 1 vs. Level 3 24.400 9 2.711 Level 2 vs. Level 3 9.600 LO 1.067