title: SPCalc: A web-based calculator for sample size and power calculations in micro-array studies.
abstract: Calculation of the appropriate sample size in planning microarray studies is important because sample collection can be expensive and time-consuming. Sample-size calculation is also a challenging issue for microarray studies because the number of genes is far larger than the number of samples so that traditional methods of sample-size calculation cannot be directly applied. To help investigators answer the question of how many samples are needed in their microarray studies, we developed a user-friendly web-based calculator, SPCalc, for calculating sample size and power for a variety of commonly used experimental designs, including completely randomized treatmentcontrol design, matched-pairs design, multiple-treatment design having an isolated treatment effect, and randomized block design.
  
  
  BACKGROUND
  The web-based calculator SPCalc is publicly available at http://www.biostat.harvard.edu /people/faculty/mltlee/webfront-r.html.
authors.affiliation: Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, 181 Longwood Avenue, Boston, MA 02115, USA. stwxq@channing.harvard.edu
authors.forename: Weiliang
authors.initials: W
authors.lastname: Qiu
authors.forename: Mei-Ling Ting
authors.initials: ML
authors.lastname: Lee