Random Drug Screen NOT SO RANDOM:

[Phaleel]

Here is the problem:
My employer holds random drug screenings 4 times a year. There is a 15% chance each year that I will be called to do a drug test. I have been called 2 out of the 3 years I have been employed. Both of those times were directly after I was on the bad side of Human Resources.
What is the chance percentage that both of these "random" drug tests were not actually random even though the employer says they were, or what are the chances that I would get called to do a "random" at 2 specific times given the information above?

Thank you for any help in advance,

Phaleel

 

[HallsofIvy]

Here is the problem:
My employer holds random drug screenings 4 times a year. There is a 15% chance each year that I will be called to do a drug test. I have been called 2 out of the 3 years I have been employed. Both of those times were directly after I was on the bad side of Human Resources.
What is the chance percentage that both of these "random" drug tests were not actually random even though the employer says they were, or what are the chances that I would get called to do a "random" at 2 specific times given the information above?

Thank you for any help in advance,

Phaleel

I puzzled by what you are saying. What do you mean that they do "random drug screenings 4 times a year" if you only have a probability of 15% of being screened in a year?

 

[Phaleel]

I puzzled by what you are saying. What do you mean that they do "random drug screenings 4 times a year" if you only have a probability of 15% of being screened in a year?

I said that because it is more specific. The chances within a year are 15%, but the split that into 4 times a year and I just so happen to have been called at very specific times right after a visit to HR.

I can do the math if it were just going the same year that I approached HR, but I had to go do a "random" the very next time after I went to HR with a problem.

Does this make sense? Let me know if I need to be more clear.

Thank you for the response,

Phaleel

 

[Phaleel]

I puzzled by what you are saying. What do you mean that they do "random drug screenings 4 times a year" if you only have a probability of 15% of being screened in a year?

Correct me if I am wrong, but is the equation as follows:

(Chance per year) * (the number of years/the number of times called) * (the number of times called right after HR visit/the amount of times I could have been called twice out of the times I could have been called) =

(.15) * (3/2) * (2/((10(10+1))/2) =

Equals a .81% chance of being called for a random after an HR visit I instigated that HR didn't appreciate twice given I've worked there for 2.5 years and they do randoms 4 times a year with a 15% chance each year of being random'd.

That sound right?

Phaleel