This article presents a new randomizing device to obtain discrete quantitative as well as qualitative data on sensitive problems. The total number of balls in the randomizing device and the ratio of the different color balls which represent different sensitive characteristics are shown to affect the efficiency of estimates
Use of the Randomized Response Technique with a New Randomizing Device
Liu, PT., Chow, LP., & Mosley, WH. (1975). Use of the Randomized Response Technique with a New Randomizing Device. Journal of the American Statistical Association, 70(350), 329-332.