If one of your employees is not very skilled with his job, would you prefer to hire a new employee to replace him or provide necessary training?

If one of my employees is not very skilled with his job, I would appoint an older employee to provide some training. If the problem still persists then I would employ a skilled employee to do the job with minimum training and avoid the loss of time and money going on an unskilled employee who should have not been employed to do that particular job (who may have been good at another job) to begin with.

First try to give him/her training and motivate. If there is no any productivity then there will be only alternative option to replace.

I strongly believe in career development. Just because an employee isn't skilled in the field of work does not mean he/she is not capable of doing the work or handling the job. It is very important that a new employee is trained, and knows what is expected of them. I agree with a previous post that a new employee should 'shadow' an older subordinate to learn and better understand what his/her job is. I also believe that a company should offer resources or training groups to effectively keep employee aware of job scope and where they should be. 

Good HRD training should payoff well down the road with this co-worker. 

From my pass experience, I think training this staff would give you best result.. also this is a way to get the trust and loyalty for that staff..

However, it's true that there is a time frame for training and giving a chance to excel and improve. So pass that time frame, proper action should be taken so as not to affect the productivity of the company. 

Practically & Theoretically Yes : Provided i see there is a X factor in him /her to rise scales . If, i would see he/she is not that worth for the organization in long run , i might think twice before calculating the plus and minus in commercial -if i loose him/her & appoint another for his/her post .

First of all, during hiring process I will make sure the candidate has sufficient job knowledge to perform the job, is a good team player, and is a quick learner. Most of the times it turned out that we had good hires, but yes it happens sometimes the candidates do not perform well. In such cases, I try to get him trained on relevant technologies/skills that are needed to perform his job, and ask one of the team members to provide guidance/help. If things still doesn't work out, then I will work with HR to get him replaced with others...

I would gladly provide the necessary training to enable him/her gain the relevant skills required to for the job.

In my opinion, if he/she is not a fast learner, I would try to give more hours of training before considering a new hire.

Good question; it is all depend up on the senior management and your company's staff policy whether to train and retain your employees for long term or use hire and fire policy to retain ONLY high potential staff and let the average and mediocre employees to leave the organisation.

help him first by training him and then decide wither he complete or replace him