期待 and 予想: looking forward and predicting a result
Compare anticipation of a library opening with predicting a game result, then read expected running time and visitor numbers as comparison points.
An awaited opening and a predicted result
期待 (きたい) means expectation or hope. “新しい図書館の開館を町の人々が期待している。” says that townspeople are looking forward to the new library's opening.
予想 (よそう) means prediction or expectation. “試合の結果を皆で予想した。” says that everyone predicted the game result together. Making a prediction does not establish the result as certain.
Reference points for length and numbers
In “期待していたよりも映画の上映時間は短かった。”, the movie's running time was shorter than expected. The comparison concerns running time.
“来場者は予想より多く、椅子を追加した。” says that more visitors came than expected, so chairs were added. 予想より supplies the comparison point, and 椅子を追加した states the action that followed.
Do not assign emotion or certainty from the word alone
The opening example shows anticipation, but the movie example compares an expected length with the actual length. Do not limit 期待 to a pleasant emotion in every use.
予想 can also concern a favorable outcome. Read what was expected and compared here without adding disappointment about the short movie or certainty that a prediction must come true.
Does 期待していたより短かった establish that the speaker disliked the movie?
Show the answer and why
No. It compares the actual running time with the expected running time. The sentence does not directly state liking, disliking, or disappointment.