Abstract Ⅰ. Introduction Ⅱ. Causality and Necessary Condition 2.1 Necessary Condition and Sufficient Condition 2.2 How to Test Necessary Condition Ⅲ. Statistical Analysis and Results 3.1 Data Collection 3.2 Validity and Reliability 3.3 Testing Necessary Condition of PEU to BI Ⅳ. Conclusion References 논문초록