Here's how my old QA department did it, based on the 5-whys

You start with the problem.

"why did we ship a fault widget?"

and find the most obvious cause, let's say:

"because Bob didn't check it properly."

Some companies would just fire Bob and call it a day, but there's no guarantee that the next guy will do any better. So you have to ask:

Why didn't Bob check it properly?

Now maybe Bob is blind, or lazy, or untrained, in which case you have to ask:

Why do we have an unsuitable person doing this important job?

Now you can start looking at your supervision and recruitment procedures. Are they good enough, were they followed, and if not, why not?

An important factor here is not to assign blame as blame ends the process without finding a solution. Blame is about assigning punishment, not preventing the problem happening again. People make mistakes when they're under pressure (as anyone who has played a computer game knows). Your processes need to allow for this and not apply too much pressure or add additional checks.

Maybe you decide Bob was the problem and replace him with Charlie - what gives you confidence that Charlie is going to be better if you don't know why Bob made the mistake? If he was blind, you could give Charlie an eye test. If he was lazy you could implement some checks to find out how many other lazy employees you have, or maybe he was pressured into signing off a rush job and didn't have the authority to stand up to his boss.

Asking 'why' five times forces you to get to the root cause - the place where a change has a good chance of preventing the problem happening again. It's important to know that 5 is just a guide, not a magic number. You keep going until you're confident that the problem won't happen again. Also the process may reveal multiple causes, and multiple things that could be improved.

I should also mention that we regularly found that a root cause was that people didn't follow the rigorous process that had been implemented after the last issue, because it was too slow. But that's OK because you can go around the cycle again and either streamline the process or look at why people decided that speed was more important than quality. Either way, you get a better understanding of the total problem.

Here's how my old QA department did it, based on the 5-whys

You start with the problem.

"why did we ship a fault widget?"

and find the most obvious cause, let's say:

"because Bob didn't check it properly."

Some companies would just fire Bob and call it a day, but there's no guarantee that the next guy will do any better. So you have to ask:

Why didn't Bob check it properly?

Now maybe Bob is blind, or lazy, or untrained, in which case you have to ask:

Why do we have an unsuitable person doing this important job?

Now you can start looking at your supervision and recruitment procedures. Are they good enough, were they followed, and if not, why not?

An important factor here is not to assign blame as blame ends the process without finding a solution. Blame is about assigning punishment, not preventing the problem happening again. People make mistakes when they're under pressure (as anyone who has played a computer game knows). Your processes need to allow for this and not apply too much pressure or add additional checks.

Maybe you decide Bob was the problem and replace him with Charlie - what gives you confidence that Charlie is going to be better if you don't know why Bob made the mistake? If he was blind, you could give Charlie an eye test. If he was lazy you could implement some checks to find out how many other lazy employees you have, or maybe he was pressured into signing off a rush job and didn't have the authority to stand up to his boss.

Just blaming Bob doesn't help because it assumes that Bob is the only person in the world that makes mistakes, and that you can replace him with someone who never makes mistakes. If you focus on why the mistake was made, and why no one else spotted it you have a better chance of avoiding it. You may also discover that you were making unreasonable demands of Bob, and that he's still the best person for the job.

Asking 'why' five times forces you to get to the root cause - the place where a change has a good chance of preventing the problem happening again. It's important to know that 5 is just a guide, not a magic number. You keep going until you're confident that the problem won't happen again. Also the process may reveal multiple causes, and multiple things that could be improved.

I should also mention that we regularly found that a root cause was that people didn't follow the rigorous process that had been implemented after the last issue, because it was too slow. But that's OK because you can go around the cycle again and either streamline the process or look at why people decided that speed was more important than quality. Either way, you get a better understanding of the total problem.

Here's how my old QA department did it, based on the 5-whys

You start with the problem.

"why did we ship a fault widget?"

and find the most obvious cause, let's say:

"because Bob didn't check it properly."

Some companies would just fire Bob and call it a day, but there's no guarantee that the next guy will do any better. So you have to ask:

Why didn't Bob check it properly?

Now maybe Bob is blind, or lazy, or untrained, in which case you have to ask:

Why do we have an unsuitable person doing this important job?

Now you can start looking at your supervision and recruitment procedures. Are they good enough, were they followed, and if not, why not?

As you can see, it often takes five steps to get to the root cause - the place where a change has a good chance of preventing the problem happening again.

  It's important to know that 5 is just a guide, not a magic number. Also the process may reveal multiple causes, and multiple things that could be improved.

An important factor here is not to assign blame as blame ends the process without finding a solution. People make mistakes when they're under pressure (as anyone who has played a computer game knows). Your processes need to allow for this and not apply too much pressure or add additional checks.

I should also mention that we regularly found that a root cause was that people didn't follow the rigorous process that had been implemented after the last issue, because it was too slow. But that's OK because you can go around the cycle again and either streamline the process or look at why people decided that speed was more important than quality. Either way, you get a better understanding of the total problem.

Here's how my old QA department did it, based on the 5-whys

You start with the problem.

"why did we ship a fault widget?"

and find the most obvious cause, let's say:

"because Bob didn't check it properly."

Some companies would just fire Bob and call it a day, but there's no guarantee that the next guy will do any better. So you have to ask:

Why didn't Bob check it properly?

Now maybe Bob is blind, or lazy, or untrained, in which case you have to ask:

Why do we have an unsuitable person doing this important job?

Now you can start looking at your supervision and recruitment procedures. Are they good enough, were they followed, and if not, why not?

An important factor here is not to assign blame as blame ends the process without finding a solution. Blame is about assigning punishment, not preventing the problem happening again. People make mistakes when they're under pressure (as anyone who has played a computer game knows). Your processes need to allow for this and not apply too much pressure or add additional checks.

Maybe you decide Bob was the problem and replace him with Charlie - what gives you confidence that Charlie is going to be better if you don't know why Bob made the mistake? If he was blind, you could give Charlie an eye test. If he was lazy you could implement some checks to find out how many other lazy employees you have, or maybe he was pressured into signing off a rush job and didn't have the authority to stand up to his boss.

Asking 'why' five times forces you to get to the root cause - the place where a change has a good chance of preventing the problem happening again. It's important to know that 5 is just a guide, not a magic number. You keep going until you're confident that the problem won't happen again. Also the process may reveal multiple causes, and multiple things that could be improved.

I should also mention that we regularly found that a root cause was that people didn't follow the rigorous process that had been implemented after the last issue, because it was too slow. But that's OK because you can go around the cycle again and either streamline the process or look at why people decided that speed was more important than quality. Either way, you get a better understanding of the total problem.