Review the item:
Julie is a real hypochondriac when her stomach
hurts, she is certain that she has a bleeding ulcer, and if she has a backache,
she believes that she has cancer of the spine.
A comma splice occurs when two complete sentences are incorrectly joined with just a comma. In the example above, no such comma exists. Julie is a real hypochondriac is one sentence. When her stomach hurts, she is certain ... begins the second sentence, which provides two pieces of evidence for sentence #1.
Because there is only empty space between the two, you should call this error a fused sentence.
To fix the problem above, you could put a period after hypochondriac and begin when with a capital W.