[LNT] Simplify population of alldata in lF_oneway

[thopre]

Summary

Use a simpler iteration to populate alldata list in lF_oneway.

[hubert.reinterpretcast]

LGTM.

lnt/external/stats/stats.py

 any number of groups.  From Heiman, pp.394-7.
 
 Usage:   F_oneway(*lists)    where *lists is any number of lists, one per
                                   treatment group
 Returns: F value, one-tailed p-value
 """
     a = len(lists)           # ANOVA on 'a' groups, each in it's own list
     alldata = []
-    for i in range(len(lists)):
-        alldata = alldata + lists[i]
+    for l in lists:
+        alldata.extend(l)
     alldata = N.array(alldata)
     bign = len(alldata)
     sstot = ass(alldata)-(asquare_of_sums(alldata)/float(bign))
     ssbn = 0
     for list in lists:
         ssbn = ssbn + asquare_of_sums(N.array(list))/float(len(list))
     ssbn = ssbn - (asquare_of_sums(alldata)/float(bign))
     sswn = sstot-ssbn