Labwork Statistics help: Average of averages

[tixi]

Homework Statement

Find the relationship between velocity and air resistance (experimentally, this is a lab course exercise)

Relevant Equations

F=mg, F(air)=1/2 p v^2 C(D) A

I have done the experiment, and have a lot of data. For each data point (we have five), we did ten repetitions, for which we need to do video analysis. The analysis works frame by frame and gives a velocity between each frame. So, to get the value of one repetition, we already need to calculate an average that has a standard deviation. THEN, to get the value for that data point, we need to find the average of these ten averages (which we can do since the number of data is the same for every point so they shouldn't be weighted). My issue here is finding the errors. How do I find the final standard deviation for a point that is calculated from 10 values which also all have some standard deviation?

Thank you in advance!

 

[haruspex]

First, are you saying the object is already expected to be at terminal velocity before the first frame?
If so, why do the two-stage averaging? Just pool them and take one average. That said, doing it in two stages should produce much the same result. You understand how to find standard error of the mean?
If not, you first need to deduce the terminal velocity in each run.