SampleSize.Youden3Grp: Sample size for the extended Youden index for three ordinal...
In DiagTest3Grp: Diagnostic test summary measures for three ordinal groups

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Calculates the sample size required to estimate the extended Youden index within a given margin of error when the diagnostic marker follows normal distributions in each diagnosis group.

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SampleSize.Youden3Grp(mu.minus, mu0, mu.plus, s.minus, s0, s.plus,
t.minus, t.plus, lam.minus, lam0, lam.plus, typeIerror = 0.05,
 margin=0.05)

`mu.minus`	A numeric value, the sample mean estimate for the mean parameter of normal distribution in D-.
`mu0`	A numeric value, the sample mean estimate for the mean parameter of normal distribution in D0.
`mu.plus`	A numeric value, the sample mean estimate for the mean parameter of normal distribution in D+.
`s.minus`	A numeric value, the sample standard deviation (SD) estimate for the SD parameter of normal distribution in D-.
`s0`	A numeric value, the sample SD estimate for the SD parameter of normal distribution in D0.
`s.plus`	A numeric value, the sample SD estimate for the SD parameter of normal distribution in D+.
`t.minus`	A numeric value, the optimal lower cut point to attain the optimal extended Youden index under normal assumptions.
`t.plus`	A numeric value, the optimal upper cut point to attain the optimal extended Youden index under normal assumptions.
`lam.minus`	A numeric value, the expected population proportion of the D_- group, used for sample size calculation. Default, lam.minus=1/3. The proportions of the three ordinal groups (lam.minus, lam0, lam.plus) should sum to 1.
`lam0`	A numeric value, the expected population proportion of the D_0 group, used for sample size calculation. Default, lam0=1/3. The proportions of the three ordinal groups (lam.minus, lam0, lam.plus) should sum to 1.
`lam.plus`	A numeric value, the expected population proportion of the D_+ group, used for sample size calculation. Default, lam.plus=1/3.The proportions of the three ordinal groups (lam.minus, lam0, lam.plus) should sum to 1.
`typeIerror`	A numeric value, (1-typeIerror)*100% confidence interval (CI) based on which the length of CI for sample size calculation will be obtained. Default typeIerror=0.05, i.e., calculate 95% CI.
`margin`	A numeric value, the margin of error on the extended Youden index estimates in sample size calculation. Default, margin=0.05.

The (1-typeIerror)% CI on the Youden index (J) estimate under normality is (J-Z_a*SE(J),J+Z_a*SE(J)), then margin= Z_a*SE(J) or half of the CI's length, where Z_a is the normal quantile, Z_a=1.95 given default typeIerror a=0.05.

Returns a numeric value indicating required sample size.

Bug reports, malfunctioning, or suggestions for further improvements or contributions can be sent to Jingqin Luo <rosy@wubios.wustl.edu>.

Jingqin Luo

Xiong, C. and van Belle, G. and Miller, J.P. and Morris, J.C. (2006) Measuring and Estimating Diagnostic Accuracy When There Are Three Ordinal Diagnostic Groups. Statistics In Medicine 25 7 1251–1273.

Youden3Grp

 mu.minus <- 6
 mu0 <- 8
 mu.plus <- 13.36


 s.minus <- 1
 s0 <- 1.2
 s.plus <- 1.4

 t.minus <- 7.02
 t.plus <- 10.52

 n <- SampleSize.Youden3Grp(mu.minus, mu0, mu.plus, s.minus, s0, s.plus,
t.minus, t.plus)