### 8. Percentiling  (here, finding percentile cutoffs for ten equal groups)

#Note, this number may differ slightly from spss, as there may be some differences
#in how percentiles are computed (Excel also differs slightly). Type=6 directly
#conforms to the SPSS method. 

quantile(Wk04$opinion, c(.1,.2,.3,.4,.5,.6,.7,.8,.9),type=6) 

##    10%    20%    30%    40%    50%    60%    70%    80%    90% 
##  4.454  5.236  6.234  9.206  9.820 10.242 10.624 11.026 11.547