Ratio of Means

  • Ronald J. Tallarida
  • Rodney B. Murray


It is common to compare the difference of two means as discussed in Procedure 39 (t-test). Sometimes it is desirable to compare the ratio of the means; for example in computing potency ratios. Discussed here is the computation of confidence limits for the ratio of two independent means (mathtype) and(mathtype). The observed ratio is \({{{{\bar x}_1}} \mathord{\left/ {\vphantom {{{{\bar x}_1}} {{{\bar x}_2}}}} \right. \kern-\nulldelimiterspace} {{{\bar x}_2}}}\), where the numerator is derived from N1 values of x and the denominator from N2 values of x. The samples are assumed to be independent and the values x normally distributed. The means \({\bar x_1}\) and \({\bar x_2}\) are also normal with variances V 1 and V 2 and covariance of zero.


Standard Deviation Confidence Interval Confidence Limit Computer Screen Individual Sample 
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Copyright information

© Springer-Verlag New York Inc. 1987

Authors and Affiliations

  • Ronald J. Tallarida
    • 1
  • Rodney B. Murray
    • 2
  1. 1.Department of PharmacologyTemple University School of MedicinePhiladelphiaUSA
  2. 2.Department of PharmacologyBiosearch Inc.PhiladelphiaUSA

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