What Is The Difference Between "Would Have Been" And "Must Have Been"?

"Would have been" - suggests a codependent relationship between an event and its causation. Using this phrase assumes certainty about causation/event  .: I.e., something is true because something else was so.  "She would have been late if she had overslept."  "You would have been cold without your coat."    Must have been - suggests only supposition (a guess) about the past event --using this phrase only implies an assumption as to what might be true, and leaves the assumption open for further confirmation:  I.e., something may have occurred because of something else.    "She must have been late because she overslept."  "You must have been cold since you had no coat."