The mean differences of audit fees among types
of auditor’s opinion may be influenced by size of
audit firms. This study is aware of this effect so that
the sample is divided into two groups; firms with Big
4 auditors and firms with non-Big 4 auditors and the
result is shown in Table 5. The results are expected
differently between both groups as indicated in the
second and third hypothesis. As reported in Table 5,
firms with Big 4 auditors show higher audit fees than
those with non-Big 4 auditors in all types of auditor’s
opinion. Firms with modified opinion (unqualified
opinion with explanation and qualified opinion) pay
higher audit fees than those with unqualified opinion
for both Big 4 and non-Big 4 auditors groups. Big 4
clients’ firms with disclaimer of opinion show lower
audit fees than those with unqualified opinion. In
reverse, non-Big 4 clients’ firms with disclaimer of
opinion report higher audit fees than those with
unqualified opinion.