Abstract: AIM: To introduce and evaluate two methods for sample size calculation in dose-response research. METHODS: The methods used for sample size calculation in dose-response research include Cochran-Armitage trend (CAT) test proposed by Jun-mo Nam and the Unified contrast (CUC) method proposed by Chang. This paper takes the example of binary data, uses the two methods to calculate the required sample size and evaluate the power by simulation under the assumption that the response rate had a linear relationship with dosage under the logit scale. RESULTS: When the probability of response followed a linear trend on the logit scale, the sample sizes estimated from the two methods are approximately equal in various parameter's settings.The simulated power of CAT test was close to the expected one, however, the simulated power of CUC method was obviously affected by the values of contrast coefficient, if a contrast whose coefficients parallel the expected response, the CUC method was more powerful. CONCLUSION: When the probability of response follows a linear trend over dosage on the logit scale, the two methods reach almost the same result, in such circumstance, the Chang's unified contrast method will obtain an increasing power.

Key words: Dose response study, Cochran-Armitage trend test, Chang's unified contrast method