Have people attack the dummy, starting from the other end of the room. Some participants will be given weapons like guns or knives, others will have to improvise with what's in the room. Measure the time it takes and use health monitoring devices to estimate the level of physical effort the participant applied.
Without doing this experiment I'm already pretty confident that a plot of time to kill will show the group given guns far ahead of the knife group or improv group. After all, they only have to aim and pull the trigger while the other groups have to move across the room. Likewise, the gun group would show far lower physical effort than the others, from the movement across the room as well as the greater need to directly apply human-sourced force. The knife group has to swing / stab / slice with enough force to meet the death conditions. The improv group has to potentially disassemble or rip apart something to then have a sharp or blunt instrument, then they still need to apply their own force like the knife group. Naturally this might change somewhat if we go nuts with the guns, like big heavy rifles or machine guns. Those would require some substantial physical effort. But handguns or the average AR-15? Not really.
Guns are a fast, low effort way to apply potentially lethal damage to a human target. You can absolutely apply lethal damage to a human in an uncountable number of other ways, but they are almost universally slower and higher effort.
Thus, we see frequent mass killings using guns, but knife incidents with high death totals are pretty rare.
"did you know that 20% of car accidents happen under the influence?
well that means in return that 80% of accidents happen with sober drivers!
i hence request immediate action and emergency beer stations to be established on all roads."
I carried a knife to school every day. Granted, I used it as a pry bar more than as a knife, and opened a lot of boxes with it, but somehow it wasn't a big deal. I brought one into show and tell in kindergarten. My father's generation kept guns at school to go hunting with after school.
Meanwhile, you can be killed without any tools, or with improvised weapons. Banning all weapons does not make an area safe. I'm not even sure it makes it safer - there are plenty of examples in US schools alone of kids being murdered (or nearly murdered) without any weapons at all.
The problem is much, much deeper than mere 'access to weapons', even supposing you could remove weapons entirely - which you can't - and that's even ignoring the fact that weapons are not a specific class of items. What makes something a weapon is how it is used. Cars are the most obvious point to make, here, but you could just as easily use a chair or anything else that gives you more reach, a harder hit, mechanical advantage to cause more damage, etc. Thinking you can look around a room and detect and remove all the weapons is ridiculous, humans are far too versatile for such a childish attitude to be effective. A room with no weapons in it has no people in it.