# Thread: random variables - expected value of time taken to perform a service

1. ## random variables - expected value of time taken to perform a service

Hello everyone,

My name is Alex, I am from Spain and I need help. I am not trained in statistics and all I know is a little bit from school and reading wikipedia, so please bear with me if I do not express myself correctly or use the most appropriate words.

I work in a service company, a hygiene B2B company; we have a number of services (such as changing the soap or washing a shower; for the case say A, B, C, D and E).

Every time one of our technicians visits a customer, he may perform one or more of them a number of times, e.g. John Doe may go to Restaurant Food and do 2A + 3C + 1D

They all carry a PDA, so I can timestamp when they go in, and when they get out, so I know the total time used to perform all the services; in the example below 2A + 3C + 1D = 320 seconds

With 380 technicians, visiting 18 customers each day, I get 6840 of these 'equations' every day. A huge sample.

Is it possible for me to somehow calculate the expected value of each service type, so I can predict how much time the technicians will take in a customer, given the services he needs to perform?

I really appreciate any help you can provide, even if just pointing me to a document or a wiki I should read or what should I google for.

All the best,
Alex

2. ## Re: random variables - expected value of time taken to perform a service

It sounds like you will need to run a multiple linear regression, if you assume that the total time for a combined service is a linear combination of individual service times.

3. ## Re: random variables - expected value of time taken to perform a service

Thank you BGM. I will read about it and see if that solves the problem.

Best regards,
Alex

4. ## Re: random variables - expected value of time taken to perform a service

Hi again,

I have read a bit about MLR and it is close to what I need, but just the opposite
Let me explain, in MLR you try to predict a value that depends on a number of variables. In my case, I have the total value, and what I need is the values of the variables (or it's expected value and, if possible, the deviation).

A real life example: a service technician goes into a public toilet and services 2 soap dispensers, 3 toilet roll holderss, 1 airfreshener and 2 sanitisers, and takes 200 seconds in and out. He then goes to the next washroom and changes 2 sanitary bins, 1 soap dispenser, 1 airfreshener and 1 sanitiser, and takes 120 seconds in doing all of these; he then goes on to the next, etc... Can I calculate how long, in average, servicing a soap dispenser takes? I have a sample as large as you may need it.

I am not even sure if this is possible!

Really appreciate any help I can get.

Best regards,
Alex

5. ## Re: random variables - expected value of time taken to perform a service

If you do it right you'll get parameter estimates for how much time each of the services contributes to the overall time. I think this is what you're looking for but don't quite get it yet - I would suggest reading a little bit more on it and maybe following along a few examples posted on the internet.

6. ## Re: random variables - expected value of time taken to perform a service

Ok, I will look into it.
Many thanks to you both.

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