I’m relatively new to PyMC, so I might be making a very simple error. A little bit about the problem I’m trying to model. There is food that is potentially contaminated which is being tested. We know the false positive and false negative rates of the testing procedure. I’m trying to get some bounds …

@ggluck Deterministic is not a random variable, it is correspondent to represent a deterministic variable (as a combination of several RVs). We can use deterministic variables to capture the transformations to the random variables and store them in the trace. However, if you can fix the determinist…

Thanks for the prompt response. I was using one data point just to test if the code was working. Here are some simulated data which should make the probabilistic model clearer. fn = .2 fp = .05 n = [100] * 200 contaminated = np.random.binomial(100,.4) not_contaminated = 100 - contaminated true_po…

[image] ggluck: I was using one data point just to test if the code was working. Of course things should work with one data point (running without an error does not mean that you’ll get the answer). The problem is that you can’t use deterministic as the likelihood. I don’t have sufficient kno…

@Nadheesh is right, the problem here is that you cannot assign observed to pm.Deterministic, in this case it is also difficult to get a close form likelihood function for the observed Positive. We are working to implement a likelihood-free algorithm (Approximate Bayesian Computation) for these case…

@ggluck : how did you end up modeling your problem?

Sum of two Binomial Distributions

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ggluck April 4, 2018, 7:07pm 6

Thanks for all your help. I appreciate the response.

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Sum of two Binomial Distributions

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