I agree with Monnie totally,

I've worked for many years as a nanny and in preschools and time outs can be very effective (on a chair, small rug, etc) but not if the child screams all the way through it and/or continues to carry on like a pork chop afterwards. Much of the point of it is for the child to realise that rotten behaviour is not acceptable and there is a consequence (having to sit still and perhaps reflect on it).

Giving a time out in a non-angry, matter of fact way and having a brief debrief afterwards is the best way I've found to modify unpleasant, tantrum attacks, and I've had a chance to practice on a lot of different kids of different ages, personalities and cultures.

Also, I find that timeouts in a fun place (like a bedroom) work less effectively than a time out in a restricted zone (like sitting on a chair or a small floor rug. One method I've used in the past with kids around 3-4 years is to sit them quietly and calmly on a small rug with a book or a toy car (just one thing, not a lot of choices) and it's up to them to sit quietly and not leave the rug for the 3-4 mins. If they do carry on, scream, leave the rug, throw things; the time out starts again. The child is not physically restrained and can walk away at any point but teaching/learning self control and consequence from the actions they choose is in my opinion, one of the most important aspects of time outs.