I have no idea about PCS-NWFP but hope the following links will help you.

http://www.cssforum.com.pk/central-s...ost102012.html

If you really want to learn Statistics then please never ever study from books by Pakistani or Indian writers.
Yes, I know they are easier to understand and they have enough stuff to get us through the ordeal of exam.
They are low cost too and easily available. But still don't touch them.

You can pass the exam with local books. But talk about real expertise and understanding of statics!
Foreign books will help you getting equipped with powerful set of tools namely logical reasoning and problem solving skills.

Books on Statistics from foreign writers will improve your analytical thinking capacity. You will have sound concepts.
Most importantly you will learn how to apply Statistical tools to analyse and solve a problem.

Having sound knowledge, good concepts, and powerful skills is more important than passing any exam.
I mean at least while studying we shouldn't look for an easy way out.

Well, enough of the grandfatherly chat, discussion on local books is given below
http://www.cssforum.com.pk/central-s...abt-stats.html

Hope it helps!