Low pass FIR filter for EEG signal
Assuming MATLAB functions to be used, passband frequency 0.15 means $\omega_p = 0.15 \pi$ whereas stopband frequency 0.2 means $\omega_s = 0.2 \pi$ and since $\omega_s &gt; \omega_p$ these settings qualify for a proper lowpass filter.

Also passband ripple being $3dB$ and stopband attenuation being $60 dB$ are valid choices (although more exact specifications requires the knowledge application requirements)

The equiripple option designs a filter in which the designed filter magnitude error is distributed accross the pass and/or stop bands in equal amounts so as to reduce the filter length to a minimum while still meeting the maximum of the allowed peak error criteria.