Hi Sultan,  I would suggest ...

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Hi Sultan, 

I would suggest using 'linear transformation' to 'normalise' the data [(X-Xmin)/(Xmax-Xmin)] which will preserve the shape of the distribution. Parametric tests can be used on non-normal data if the sample size criteria can be met, more info at http://blog.minitab.com/blog/adventures-in-statistics-2/choosing-between-a-nonparametric-test-and-a-parametric-test. So the answer to your question is that it is not essential to have normally distributed data. I agree with others on not forcing a particular distribution on the data  - use as is / find the distribution that fits your data.