All calculations are associated with some level of uncertainty which we define as its **error**.

Concept #1: Error can be categorized as either **systematic** or **random**.

Example #1: A uncalibrated pipet is used in the titration of 25 mL of 0.250 M KMnO_{4} with 50.0 mL of HNO_{3}. If the pipet delivers 23.120 +/- 0.02 mL what can be said about the possible error(s) observed?

Example #2: State whether the errors are random or systematic for each of the following:

a) The analytical measuring pipet in the lab consistently delivers 25.0 0.03 mL.

b) I weigh an analyte sample 4 times and obtain the following numbers: 1.110, 1.392, 1.040 and 1.850.