# Probability density functions

1. Jul 16, 2010

### jamie516

This could go in the homework section I suppose, but I couldn't follow the guidelines, so I'll try asking it here.

The attached image is a probability distribution for measured fibre angles from a spray up carbon fibre process. This is in a report that I need to explain. To get the probability distributions on the Y axis, would one just add up all the fibres, and divide that total by the number between a given orientation?

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• ###### probability distribuitions.jpg
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2. Jul 16, 2010

### stewartcs

I'm not sure what you are asking. The data appears to follow a Gaussian Distribution (i.e. Normal Distribution). The way to interpret the graph is like this: For the 6k 115mm fibers, there is a 0.29 probability that the in-plane fiber orientation is approximately 0.0 radians.

CS

3. Jul 17, 2010

### jamie516

I'm asking how would generate the probabilities on the Y-axis?

4. Jul 17, 2010

### stewartcs

Your graph shows the y-axis as "probability" already. So there's nothing to generate.

CS

5. Jul 18, 2010

### jamie516

I know it does, what I'm asking is how was it obtained in the first place? Would you just add up the number of fibres between a certain angle and then divide by the total number of fibres? And that gives probability?

6. Jul 18, 2010

### brewnog

It's generated by looking at all the fibres, putting each one into a category (of orientation), and counting up how many fibres are in each category; then expressing that number as a proportion of the total number of fibres.

This should have been posted in homework help.

7. Jul 18, 2010

### jamie516

Yes, that's what I thought, thanks for your help, maybe it can be moved?