An experimental setup, based on a plastic scintillator with an embedded wavelength shifter fibre and photosensors at the two ends, has been used to detect cosmic muons in undergraduate laboratory activities. Time and amplitude information from the two photosensors were measured using the time-over-threshold technique. The distribution of the energy deposit in the scintillator was measured under different shielding conditions in the same building and evaluated by simple calculations. A GEANT simulation taking into account the angular distribution of the incoming muons, the shielding material above the setup and the response of the detector was also compared to the data. (Contains 6 figures.)