Calculations and Data Managment:
All calculations were performed on an Intel Pentium-based microcomputer with
a clock speed of 1800 MHz.
Statistical calculations were made with Statgraphics Plus for Windows Version
4.1, Manugistics, Inc., Rockville, MD
Data management was carried out using
Microsoft Access 97, SR-2 (Microsoft Corporation, Redmond, WA)
Microsoft Excel 2002 (Microsoft Corporation, Redmond, WA)
DBase III Plus database (Ashton-Tate, Culver City, CA).
StatXact-4 for Windows 4.0 ( Cytel Software Corporation, Cambridge, MA).
LogXact-Turbo Version 1.1
Two-tailed tests and a type I error rate of 0.05 were employed throughout.
Visual Analog Scale
Huskison, E.C., Melzack, R. (ed). Visual Analog Scale. In Pain Measurement
and Assessment. Pp. 33-37. New York, Raven Press, 1983.
Huskison EC: Visual Analog Scales: In pain measurement and assessment, Melzack
R ed. New York, Raven Press, 1983, p 33-37.
Bond MR: Pain - Its Nature, Analysis and Treatment. New York,
Churchill Livingstone, 1979, p 26-30.
Bond A, Lader M: The use of analogue scales in rating subjective feelings.
Br J Med Psychol 1974;47:211-218.
Babbie ER: Survey Research Methods, ed 1. Belmont, Wadsworth
Inc, 1973, p 131-156.
Huskison, E.C., Melzack, R. (ed). Visual Analog Scale. In Pain Measurement
and Assessment. Pp. 33-37. New York, Raven Press, 1983.
Exact Chi-Square
Radlow R, Alf EF: An alternate multinomial assessment of the accuracy of
the Chi-Square test of goodness of fit. Journal of the American Statistical
Association, 1975:70:811-813.
Spearman rank correlation procedure
Sokal, R.R., Rohlf, F.J. Nonparametric Tests for Association. In Biometry,
pp. 601-616. New York: W. H. Freeman and Company, 1981.
Marquardt algorithm
Marquardt DW: An algorithm for least squares estimation of non-linear models.
J Soc Indust Appl Math 1963;11:431-441.
Wilk's test
Kendall M, Stuart A, Ord JK: Tests of hypotheses in multivariate analysis.
in, The Advanced Theory of Statistics, ed 4. London & High Wyncombe, Charles
Griffin & Co., 1983, 295-319.
Wilks SS: Sample criteria for testing equality of means, equality of variances
and equality of covariances in a normal multivariate distribution. Ann Math
Statist 1946;17:257-281.
Student's t distribution
Zar JH: One-sample hypotheses: Biostatistical Analysis, ed 2. Englewood Cliffs,
NJ Prentice-Hall, Inc., 1984, p 97-121.
Two sample power analysis
Zar JH: Two-sample hypotheses: Biostatistical Analysis, ed 2. Englewood Cliffs,
NJ Prentice-Hall, Inc., 1984, p 122-149.
CI for difference in medians
Lehmann, EL, D'Abrera, HJM: Comparing two treatments or attributes in a population
model. in:, Lehmann, EL, D'Abrera, HJM, Nonparametrics: Statistical Methods
Based on Ranks, Holden-Day, Inc., Oakland, CA, pages 55-119., 1975,
One-Factor ANOVA
Zar JH: Multisample hypotheses: The analysis of variance: Biostatistical Analysis,
ed 2. Englewood Cliffs, NJ Prentice-Hall, Inc., 1984, p 162-184.
Two-factor ANOVA
Zar JH: Two-factor analysis of variance: Biostatistical Analysis, ed 2. Englewood
Cliffs, NJ Prentice-Hall, Inc., 1984, p 206-235.
Linear regression analysis
Rice JA: Linear least squares in Mathematical Statistics and Data Analysis,
Pacific Grove, CA, Wadsworth & Brooks/Cole Advanced Books and Sortware,
1988, p 453-510.
ANOVA
One-factor ANOVA after logarithmic transformation was used to evaluate differences
among groups.
Generalized Linear Models.
McCullagh P, Nelder JA. An Outline of Generalized Linear Models. In, Generalized
Linear Models (2nd Edition), Chapman & Hall, London, 1989, Pp. 21-47.
Resampling Differences among Medians
Good PI: Testing Hypotheses. In Permutations: A Practical Guide To Resampling
Methods For Testing Hypotheses, New York, NY, Springer-Verlag, 1994 pp 24-43.
Neuman-Keuls procedure
Newman D: The distribution of range in samples from a normal population, expressed
in terms of an independent estimate of standard deviation. Biometrika 1939;31:20-30.
Keuls M: The use of the "studentized range" in connection with an analysis
of variance. Euphytica 1952;1:112-122.
Confidence intervals of variances of the residuals
Zar JH: Confidence Limits for the Population Variance. in, Biostatistical
Analysis, ed 2, Englewood Cliffs, NJ, Prentice Hall, Inc. 1984, 115-116.
Confidence intervals of a proportion
Zar JH: Confidence Limits for proportions. in, Biostatistical Analysis, ed
2, Englewood Cliffs, NJ, Prentice Hall, Inc. 1984, 378-380.
Agresti A: Two-Way Contingency Tables, In: An Introduction to Categorical
Data Analysis. 1996, John Wiley and Sons, New York, 16-52.
Confidence intervals of difference between two proportions
Zar JH: The binomial distribution. in, Biostatistical Analysis, ed 2, Englewood
Cliffs, NJ, Prentice Hall, Inc. 1984, 369-405.
Exact confidence interval on the difference of proportions.
Berger RL, Boos DD
P-values maximized over a confidence set for the nuisance parameter. Journal
of the American Statistical Association 1994; 89: 1012-1016.
Tukey procedure
Kirk RE: Multiple comparison tests. In Experimental Design, ed 2.
Belmont, Wadsworth Inc., 1982, p 90-126.
Kendall's coefficient of concordance
Kendall MG, Babington-Smith B. The problem of m rankings. Ann Math
Statist 1939;10:275-287.
Logistic Regression:
Kleinbaum DG (1994). Logistic Regression: A Self-learning Text. New York.
Springer-Verlag, Inc. [Chapter 8 Analysis of matched data using Logistic Regression
pp 227-252.
Multivariate logistic regression using conditional exact inference
on the parameters of the model will be used for analysis[*Kleinbaum, ch8,
hirji 87]. Abuse status will be used for the response variable and all other
collected variables will be considered for inclusion as explanatory variables.
Odds ratios and two sided confidence intervals will be calculated using standard
methods. Logistic models of this complexity typically require approximately
75 pairs of subjects.
Hirji KF, Mehta CR, Patel NR. (1987). Computing distributions for exact logistic
regression. JASA, 82:1110-1117.
Agreement:
Agresti A: Models for matched pairs, In: An Introduction to Categorical Data
Analysis. 1996, John Wiley and Sons, New York, 226-256.
Altman DG, Bland JM: Measurement in medicine: The analysis of method comparison
studies. The Statistician 1983;32:307-317.
Bland JM, Altman DG: Statistical methods for assessing agreement between two
methods of clinical measurement. Lancet 1986;1:307-310.
Flack VF: Measuring agreement for multinomial data. Biometrics 1987;38:1047-1051.
Fleiss JL: The measurement of interrater agreement, In: Statistical Methods
for Rates and Proportions. 1981, John Wiley and Sons, New York, 212-236.
Fleiss JL: Measuring nominal scale agreement among many raters. Psychological
Bulletin 1971;76:378-372.
May SM: Modelling [sic] observer agreement–an alternative to kappa. J Clin
Epidemiol 1994;47:1315-1324.