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sassymenace
Level II

Probit Analysis & Fit Testing

I am using the Simple Probit Analysis script add-in to determine LD50, LD90, and LD95.

 

Is this script capable of correcting with Abbott's, or how do you set this up?  Currently, I corrected the data myself by applying the Abbott's correction to the raw data to adjust for mortalities.

 

After running the Probit Add-In, how do I determine goodness of fit?  There are no Chi Squared results.  Is there another way I can run this analysis to get my LD values, as well as getting the Chi Square? 

33 REPLIES 33
sassymenace
Level II

Re: Probit Analysis & Fit Testing

Do I use # of deaths as my response then?  My "Start" is how many live counts I have before treatment is applied. The 15 min column is deaths.  Is this correct, or do I need to use live counts as my response?

 

Do I need to apply LOG to the Dose with the Transform drop down, or is this analysis fine without it? 

Re: Probit Analysis & Fit Testing

Please see my reply with a complete analysis that ends with the question, "So we agree now, no?" It shows you how to set up your data in a JMP data table. It also shows you how to assign the data columns to the analysis roles in the Fit Model launch dialog and change the other settings for a proper Probit analysis. I did not apply any transformation to the dose levels - it is unnecessary.

sassymenace
Level II

Re: Probit Analysis & Fit Testing

Thank you!  I was tripped up when you said to not include mortality rate, so I was double checking if I was supposed to be using death or live counts as the response.  Hopefully I won't have anymore major issues!

 

Truly appreciate the help!

Re: Probit Analysis & Fit Testing

We already determined that you do not have life time or time to event data. You have a case of dose-response data. You collected observations at 15 minutes, so time is fixed. You counted the number of deaths and the total number subjects at each dose. This case is handled by GLM as I showed you. Please disregard the example based on life time that used Life Distribution. Survival analysis methods do not apply here. You should use a Probit analysis as you first started.