How to count IC50 - (Oct/28/2000 )

I have got the result of MTT assay, How can I count IC50, thank you

Dear STUDENT:

Dear Student:

You may try plotting the logOD versus log drug concentration. Find 50% of control cells OD value and that will be IC50%. good luck

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This is my problem, too. I am a student in Iran working on some tumor cell lines, by performing MTT assay.