24.02.2013 Views

Optimality

Optimality

Optimality

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

68 C. Cheng<br />

root MSE<br />

bias<br />

0.0 0.04 0.08 0.12<br />

-0.15 -0.05 0.05 0.15<br />

Models 1,3,5,9; sigma=3<br />

0.82 0.86 0.90 0.94 0.98<br />

true pi0<br />

Models 1,3,5,9; sigma=3<br />

0.82 0.86 0.90 0.94 0.98<br />

true pi0<br />

root MSE<br />

bias<br />

0.0 0.015 0.030 0.045 0.060<br />

-0.15 -0.05 0.05 0.15<br />

Models 2,4,6,10; sigma=1<br />

0.82 0.86 0.90 0.94 0.98<br />

true pi0<br />

Models 2,4,6,10; sigma=1<br />

0.82 0.86 0.90 0.94 0.98<br />

true pi0<br />

Fig 3. Root MSE and bias of the π0 estimators by Benjamini and Hochberg [3] (circle), Storey<br />

et al. [31] (triangle), and (3.1) (diamond)<br />

and the bias of the proposed and the Benjamini and Hochberg’s estimators are<br />

reduced substantially while the small downward bias of Storey’s bootstrap estimator<br />

remains. Overall the proposed estimator (3.1) outperforms the other two estimators<br />

in terms of MSE and bias.<br />

Next, operating characteristics of the adaptive FDR control ([3]) and q-value<br />

FDR control ([31]) at the 1%, 5%, 10%, 15%, 20%, 30%, 40%, 60%, and 70%<br />

levels, the criteria API (i.e., the HT(�α ∗ cal ) procedure) and Ip ([7]), are simulated<br />

and compared. The performance measures are the estimated FDR (�FDR) and the<br />

estimated false nondiscovery proportion ( FNDP) � defined as follows. Let m1 be the<br />

number of true alternative hypotheses according to the simulation model, let Rl be<br />

the total number of rejections in simulation trial l, and let Sl be the number of<br />

correct rejections. Define<br />

�FDR = 1<br />

1000<br />

FNDP � = 1<br />

1000<br />

� 1000<br />

l=1 I(Rl > 0)(Rl− Sl) � Rl<br />

�1000 l=1 (m1− Sl) � m1,<br />

where I(·) is the indicator function. These are the Monte Carlo estimators of the

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!