Explosives Simulation (1-prop z)

A company claims to have invented a hand-held sensor that can detect the presence of explosives inside a closed container. Law enforcement and security agencies are very interested in purchasing several of the devices if they are shown to perform effectively. An independent laboratory arranged a preliminary test. If the device can detect explosives at a rate greater than chance would predict, a more rigorous test will be performed. They placed four empty boxes in the corners of an otherwise empty room. For each trial they put a small quantity of an explosive in one of the boxes selected at random. The company’s technician then entered the room and used the sensor to try to determine which of the four boxes contained the explosive. The experiment consisted of 50 trials, and the technician was successful in finding the explosive 16 times. In the dot plot below, each dot represents the proportion of times (out of 50) that the technician successfully found the explosive, under the assumption that they should find it 25% of the time (just guessing). Does this simulation indicate that the device is effective in sensing the presence of explosives, and should undergo more rigorous testing?