scale of measurements in sign test and signed rank test Can some one help me to understand the right scale of measurement to use in sign test as well as in signed rank test? 
I read a certain book it says nominal scale is used in sign test while ordinal scale is used in the signed rank test, the other online material says ordinal scale is used in both sign test and signed rank test. I'm confused.
 A: (Moving comment to answer)
Strictly, the signed rank test is designed to be used on continuous random variables, since you need to be able to rank the differences, and in the usual tables the different arrangements of signs to ranks are assumed to be equally probable under the null.
If the original data that form pairs are only ordinal, it's not really possible to assign ranks (what's the relative ranking of "High minus medium" vs "medium minus low"?)
The sign test arguably also assumes continuity, but if the proper account is made of ties, it can be adapted to deal with ordinal data.
A: simple sign test use nominal scale data while signed rank test uses ordinal scale data. i am a stats major student and i am currently studying these tests. I hope your confusion is cleared.
for more info consult these books
chahudary, S.M. and kamal, S. (2010), " intorduction to statistical theory" part 1 &2, 8th ed., ilmi kitab khana, Lahore, Pakistan
walpole, R.E., Myers, R.H. and Myers, S.L (2011, " Probability and statistics for engineers and scientist" 9th ed., Prentice Hall, NY
