2016 Update

Task/Statistics-Basic/J/statistics-basic-1.j

@@ -1,7 +1,7 @@
-   require'statfns'
-   (mean,stddev) ?1000#0
+   require 'stats'
+   (mean,stddev) 1000 ?@$ 0
 0.484669 0.287482
-   (mean,stddev) ?10000#0
+   (mean,stddev) 10000 ?@$ 0
 0.503642 0.290777
-   (mean,stddev) ?100000#0
+   (mean,stddev) 100000 ?@$ 0
 0.499677 0.288726

Task/Statistics-Basic/J/statistics-basic-2.j

@@ -1,3 +1,3 @@
 histogram=: <: @ (#/.~) @ (i.@#@[ , I.)
 require'plot'
-plot ((%*1+i.)100) ([;histogram) ?10000#0
+plot ((% * 1 + i.)100) ([;histogram) 10000 ?@$ 0

Task/Statistics-Basic/J/statistics-basic-3.j

@@ -1,23 +1,24 @@
 histogram=: <: @ (#/.~) @ (i.@#@[ , I.)
 
-meanstddevP=:3 :0
+meanstddevP=: 3 :0
   NB. compute mean and std dev of y random numbers
   NB. picked from even distribution between 0 and 1
   NB. and display a normalized ascii histogram for this sample
-  NB. note: should use population mean, not sample mean, for stddev
+  NB. note: uses population mean (0.5), not sample mean, for stddev
   NB.       given the equation specified for this task.
   h=.s=.t=. 0
-  buckets=. (%~1+i.)10
-  for_n.i.<.y%1e6 do.
-    data=. ?1e6#0
-    h=.h+ buckets histogram data
-    s=.s+ +/ data
-    t=.t+ +/(data-0.5)^2
+  chunk=. 1e6
+  bins=. (%~ 1 + i.) 10
+  for. i. <.y%chunk do.
+    data=. chunk ?@$ 0
+    h=. h+ bins histogram data
+    s=. s+ +/ data
+    t=. t+ +/ *: data-0.5
   end.
-  data=. ?(1e6|y)#0
-  h=.h+ buckets histogram data
-  s=.s+ +/ data
-  t=.t++/(data-0.5)^2
-  smoutput (<.300*h%y)#"0'#'
-  (s%y),%:t%y
+  data=. (chunk|y) ?@$ 0
+  h=. h+ bins histogram data
+  s=. s+ +/ data
+  t=. t+ +/ *: data - 0.5
+  smoutput (<.300*h%y) #"0 '#'
+  (s%y) , %:t%y
 )