Final answer:
In p-chart calculations, the assumption is that the sample size is fixed, which ensures consistency in statistical quality control.
Step-by-step explanation:
An assumption in a p-chart calculation is that the sample size is fixed. This means that the sample size does not change over time and is the same for each sample taken. A p-chart is used in statistical quality control to monitor the proportion of defective items in a process and to determine whether the process is in a state of control.