  Context and Motivation: Software requirements are affected by the knowledge
and confidence of software engineers. Analyzing the interrelated impact of
these factors is difficult because of the challenges of assessing knowledge and
confidence.
  Question/Problem: This research aims to draw attention to the need for
considering the interrelated effects of confidence and knowledge on
requirements quality, which has not been addressed by previous publications.
  Principal ideas/results: For this purpose, the following steps have been
taken: 1) requirements quality was defined based on the instructions provided
by the ISO29148:2011 standard, 2) we selected the symptoms of low qualified
requirements based on ISO29148:2011, 3) we analyzed five Software Requirements
Specification (SRS) documents to find these symptoms, 3) people who have
prepared the documents were categorized in four classes to specify the
more/less knowledge and confidence they have regarding the symptoms, and 4)
finally, the relation of lack of enough knowledge and confidence to symptoms of
low quality was investigated. The results revealed that the simultaneous
deficiency of confidence and knowledge has more negative effects in comparison
with a deficiency of knowledge or confidence.
  Contribution: In brief, this study has achieved these results: 1) the
realization that a combined lack of knowledge and confidence has a larger
effect on requirements quality than only one of the two factors, 2) the
relation between low qualified requirements and requirements engineers' needs
for knowledge and confidence, and 3) variety of requirements engineers' needs
for knowledge based on their abilities to make discriminative and consistent
decisions.
