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Personality shares a close bond with character building. Students who are learning about character building may be able to apply the principles of environmentally friendly behaviors on everyday life. Personality instrument is ome of the most common ways to measure environmental personality, and one of the most important attributes on a test/instrument is validity. Item validity is used in item analysis to improve on the measurement, where accurate measurement is not only achieved through the function of the item description but also through the effects on the number of options and sample size. This study aims to discover the difference in item validity on the students environmental personality. The variable used in this research is the number of options (3 and 5) and sample size (175 and 215). The data is analyzed using two way ANOVA followed with  HSD post hoc test. The results of this study shows that: (1), Number of options influenced item validity of the students environmental personality score (2), sample size did not influence the item validity of the students environmental personality score and (3) there is an interacting influence betwern the number of options and sample size on the item validity of the students environmental personality. The HSD test reveals that the sample group with 175 students that used 3 options differs significantly compared to the other groups, while there is no significant difference between other student groups working with either 3 or 5 options. To summarize, the item validity of students environmental personality is better on groups 175 samples working with 3 options rather than 5 options or on groups of 215 students working with either 3 or 5 options.

Item Validity; Environmental Personality; Number of options; Sample size