Answer:
Error of measurement
Explanation:
The results could be a result of an error in measurement. One error can be the parallax error. This is an error that results when the measurement is different from the different measurement. An example will be a person reading the meniscus of the water from different angles. In addition, the error can be inbuilt instrument error. Also, the rubber duck might have gained a bit of water in the first measurement which added to the second reading.