  The OFDM waveform exhibits high fluctuation in the signal envelope which
causes distortion in the nonlinear power amplifier of the transmitter.
Peak-to-Average Power Ratio (PAPR) and Cubic Metric (CM) are the common metrics
to quantify the phenomenon. A promising approach for PAPR or CM reduction is
Sign Selection which is based on altering the signs of the data symbols. In
this paper, the Method of Conditional Expectations (CE Method) is proposed to
obtain a competing suboptimal solution to the Sign Selection problem. For PAPR
reduction, a surrogate metric is introduced which allows for an efficient
application of the CE Method. For CM reduction, the tractability of the
definition of CM is exploited to this end. The algorithm is analyzed to obtain
an upper bound on the worst-case reduced metric value. A noticeable
characteristic is the persistent reduction capability for a wide range of
subcarrier numbers. In particular, simulations show a reduction of the
so-called "effective PAPR" to about 6.5 dB from 10.5 dB and 11.7 dB
respectively for 64 to 1024 subcarriers. A similar steady reduction of 3 dB is
observed for CM. In addition, the CE Method leads to a pruned version of Sign
Selection which halves the rate loss.
