I would like to conduct a research to measure inter- & intra-subject reliability (less than 30 subjects) in preparing 3 types of fluids (A, B, C).
Each subject will prepare fluid A for 3 times, followed by fluid B & C.

My questions are:
1. How to measure inter-subject reliability?
Should I ask the subjects to prepare 3 types of fluids again or I just need to calculate the mean values for each type of fluids they’ve prepared in 3 trials?

2. Which statistical test should I use to measure the inter- & intra-subject reliability?

Hope someone can help me. I will be using SPSS.