The I Ching is an intuitive tool that always points to growth and personal empowerment. Using the I Ching is justified every time there is a legitimate need for guidance, insight,
creativity, wisdom, or prediction.
Appropriate use
The more thought is put into a question, the more insights will be revealed in the response. And knowing that many possible questions have an answer tends to make one’s mind more curious, inquisitive, and open to possibilities. So an appropriate use of the I Ching does not replace thinking but actually stimulates it, and then transcends it.
Inappropriate Use
However, having selfish motives, asking frivolous questions, doing excessive or unnecessary readings about a subject, ignoring difficult or unfavorable responses, or knowingly avoiding essential questions are misuses of the I Ching that may result in irrelevant responses.
In conclusion, as with any language, practice is necessary to develop a “feel” for the answers and their nuances and make sense of apparently incomprehensible responses. In fact, The Logic of Chance could not have been written without the experience gained from innumerable I Ching readings.
I Ching Interpretation 
I very much like the clarity expressed here. It helps to know what is a good question and what will be likely to provide a good answer.
Robert: Does the author believe the I Ching can be used to help in making business decisions? How about investment decisions?
Yes, I believe that the I Ching can be used in making legitimate business or investment decisions, as long as no harm will be caused to another person.