Guesswork (noun)

1. The act or process of making an estimate or a prediction based on incomplete information.
2. An estimate or prediction made based on incomplete information.

Origin:

From the verb guess + work.

Examples:

1. The detective was able to solve the case with little guesswork.
2. He had to make a guesswork when the facts were not clear.
3. The forecast was based on a lot of guesswork.
4. The estimate was just a guesswork and not accurate.
5. The stock market prediction was based on guesswork.