The object of this research is to find the effectiveness of using collaborative writing method to improve students’ writing skill, especially for descriptive text at the eight grade students of Mts. Mathalibul Huda Mlonggo academic year 2018/2019. The subject of this research were 56 students.
Experimental research was used as a method in this reserach. The reseach was conducted in two groups, they are experimental group and control group. The experimental group was students which were taught by collaborative writing method, while the control group was students which were taught without collaborative writing. The data gathered through post-test.
The result of the research showed that collaborative writing is effective to use in teaching writing skill in descriptive text. The score of experimental group (85,35) is higher than the control group (36,25). From the result of statistic calculation, it was obtained that the value of t-observation (to) 2,94 and degree of freedom (df) is 54. In table of significant 5%. The value of degree significance is 1,67. Comparing those velues, the result 2,94> 1,67. Which mean t-observation (to) score is higher than t-table (tt) score. In other words, the alternative hypothesis (Ha) is accepted and the Null Hypothesis (Ho) is rejected. Therefore, teaching writing skill in descriptive text by using Collaborative writing method is effective.