PINT and PPINT: Power In Two-level Designs.
Version 1.61 (April, 1999)

PINT program calculates formulae for the paper by Tom A.B. Snijders and Roel J. Bosker,
Standard Errors and Sample Sizes for Two-Level Research,
Journal of Educational Statistics, vol. 18, 1993, 237 - 259.

You run the program just by giving the command PINT.
The default name for the input file is AX.DAT.

PPINT interactively makes an input file (such as AX.DAT) for PINT.

PINT writes output to files AX.SER (main output: standard errors)
                        and AX.COV (secondary output: covariance matrices).
Other files for input and output can be chosen by mentioning them
on the command line.
E.g., the command
  PINTN  PARAM.IN  RESULTS.SE RESULTS.COV
will read input from PARAM.IN and write output to RESULTS.SE and RESULTS.COV.

If you are a new user, it is easiest to use PPINT.
Below follow  the requirements for the input file AX.DAT for PINT,
for those who wish to use PINT directly.

Number of level-1 units per level-2 unit is n;
number of level-2 units is N;
output is given for all maximal (n,N) combinations satisfying N(n+c) <= k,
  where k is given in input file, 
  n goes from nmin to nmax in steps of nstep,
  and where nmin, nmax, nstep are given in input file.

The input file (AX.DAT) can be written by any ASCII text editor according
to the specification given below, or it can be written interactively
by the program PINTIN, described in readme2.txt.

File AX.DAT should contain
(symbol used in paper is indicated between parentheses):
* Number of level-1 variables (not including the constant variable)
* Number of level-1 variables with only a fixed effect
* Number of level-2 variables (not including the constant variable)
* nmin
* nstep
* nmax
* total sampling budget (k)
* relative sampling costs per level-2 unit (c)
  (where sampling costs per level-1 unit is unity)
* residual variance on level 1 (sigma-squared);
* lower diagonal covariance matrix of random effects (tau_2);
* lower diagonal within-groups covariance matrix (SIGMA-W);
  (order of variables: first fixed effects variables,
                       then constant, then random effects variables);
* lower diagonal between-groups covariance matrix (SIGMA-B);
  (order of variables: first constant, then real level-2 variables,
                       then group means of level-1 variables);     
* means of level-1 variables (mu_1);
* means of level-2 variables (mu_2).

The lower diagonal matrices are read as one matrix row per input line.
(In other words: after reading the diagonal element, the program passes on
 to reading the next line.)
All other input elements are read in free format.
The first 8 input variables (up to the value of c) should be integers
(no decimal point). The other variables are read as real numbers
(may, but need not, contain a decimal point.)

The user must take care that the second moment matrices to be inverted
are non-singular. (If they are not, the program will run into an error.)

A possible input file AX.DAT is as follows:

2 1 1
10 1 100
1000  5
0.5
 0.09
 -0.01 0.0075
 0.8
 0.3  1
 1
-0.13  0.2
0
0

Questions can be addressed to :
Tom A. B. Snijders
Department of Statistics and Measurement Theory
University of Groningen
Grote Kruisstraat 2/1
9712 TS Groningen
The Netherlands
Email T.A.B.SNIJDERS@PPSW.RUG.NL

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