The aim of this research is to find out the effectiveness of mystery game for teaching writing. This research was conducted at SMK N 3 Purwokerto in academic year 2014/2015.
This research used quasi experimental. The subjects of this research were class X Hotel Accommodation 1 as the control group and X Hotel Accommodation 2 as the experimental group. Mystery game was implemented to the experimental class while the control class was taught by classical method of teaching. Test was used to collect the data. The tests used were pre-test and post-test which were in the form of essay test. T-test formula and interrater reliability were used to analyze the data.
The result showed that students’ ability of the experimental class was higher than the control class. It could be seen on the t-test result computation , where the t-test result was 3.93 and t-test table was 1.68 in degree of freedom 50 at the significant level 0.05. The result was higher than t-table (3.93>1.68). It means that the hypothesis stated that mystery game is effective for teaching writing was true proved.