A mail survey was used for data collection. After five weeks, we sent 600 questionnaires to CPAs. We received 131 usable questionnaires, that four were missing and thirty mails returned the survey found unanswered because CPAs are not working in accounting firm. Thus, the response rate was 23%. According, Aaker, Kumar and Day, (2001), they suggest response rate for a mail survey, without an appropriate follow-up procedure, is less than 20%. Thus, the response rate of this study is acceptable. Additional, non-response bias was investigated separate half 50% return first and last by t-test, and results were not significant. Therefore, we were implied that these received questionnaires as non-response bias