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Although I don't doubt that McDonald's ripped off Brad, I hardly think \"weighing yourself with and without the bag\" is a scientific way of obtaining the true weight of the bag. I would be very curious what the real weight of the bag was.
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@Radi0logy: Well, if he had to do it by this method, at least it would have been more accurate to simply not get on the scale himself, and pile all 5 bags he bought on the scale together. Then divide by 5.
I'm sure that would give a less dramatically underweight answer.
@Radi0logy: It is scientific. It's called \"Tare\".
@AliyaBabasaur: Uncalibrated consumer weight scale. Get a calibrated, certified scale made for commercial/trade use., and you won't have that problem.
@HiPwr: Consumer weighting scales are made to be accurate and most responsive for above 50lbs. The size of scale on the markings make it hard to get accurate, to the pound readings instead of 5/10lb readings.
@Radi0logy: On the other hand, OP does not need the same accuracy and certification that a scientific lab needs. That 20 dollar off the shelf Walmart scale does just fine for a rough estimate, and 4lbs of a 10lb bag is pretty big discrepancy enough to say, OP was ripped off. Even more, its ludicrous to believe that you would need to use a scientific or certified scale to reweigh something that was probably never weighed with one in the first place. He needed accuracy to pounds, not ounces or grams.
@silver-bolt: Im aware of what tare is, but you don't seem to --
\"Definitions of 'tare' (târ)
The American Heritage® Dictionary
(noun)
1) The weight of a container or wrapper that is deducted from the gross weight to obtain net weight.\"
Maybe you can read in there the part where it says a \"container or wrapper\", of which some guy standing on a scale is neither. The point of a tare is that the object holding the second object being weighed is unmoving, immobile, and does not fluctuate in its weight readings. Sorry to tell you this, a human is none of those things.
@Piaculum: Incorrect, but thanks for joining in the discussion.
@jswilson64: Also incorrect. If part of the methodology is flawed, the entire experiment is worthless.
@OnceWasCool: Its called reading. Try it sometime.
@Radi0logy: Ok I wasted a few minutes testing this for myself, I had to use a big bag of rice cause it was heavy enough to weigh on the scale by itself. Not sure if something that weighs less produces a larger margin of error or smaller margin of error.
In my tests, the bag of rice fluctuated between 12 pounds and 18.5 pounds with me holding it, over 5 trials. When I weighed the bag by itself it fluctuated between 16 and 16.5 pounds. So could have undermeasured by as much as 4.5 lbs or overmeasured by as much 2 lbs. Clearly, this is a result of the movement of the human body, the positioning of the feet on the scale, the floor and other unknown factors.
Feel free to continue to argue with me, but until you perform your own tests that show otherwise, I don't care. I'm still curious to see someone do this with ice, as I feel relatively certain the margin of error would be larger, what with the more unpredictable shape that ice blocks take.
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Per my comment above: get a 10 lb weight. They sell 30 lb dumbbell sets at Target relatively cheap and you can use them afterward to help work off some of the McNuggets you no doubt will buy on impulse when getting ice. Get a plank, center it, tie ice to one end and 10 lb weight to other end. No more laborious dissertations on tare, bathroom scales and the obligatory insults and flaming that even a ridiculously stupid internet discussion attracts when there are more than 5 replies.
@ManiacalV: I assume this is targeted at me? First of all I have no intention of spending a penny of my own money for the sake of this silly internet argument. Secondly, although I have never been in the McDonalds near me, I doubt they sell ice. Third, your experiment doesn't take into account the precision of the centering, the specific weight of each end of the plank, or differences in the angle of the wood of the plank from one end to the other. Fourth, even ignoring all of the problems mentioned above, it only implies that the ice weighs less than 10lbs, not by what margin. Without knowing how far under 10lbs the ice is, it is almost completely worthless. (I would wager this would never have been posted if the bag had been above 9lbs in weight. It was only the apparently gross difference that prompted its posting)
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Let's see...you weigh 200 yourself. It says 200 pounds then you immediately pick up the bag of ice and without removing anything on your person weigh yourself again. It says 206.2 pounds. Hmm.....206.2 pounds - 200 pounds. What could that be??? Hmmmm...6.2 pounds!! That is, unless the scale fairy snucked in there and readjusted the scale.
What he did was correct. You are an idiot.
@savdavid: Yep I'm an idiot. Go buy a bag of ice, weigh it the way the OP did, balancing precariously on a bathroom scale (of quality or age that none here know), and then find the weight using an appropriate scale.
Please note that no where in my post did I indicate that there was a problem with his math, dumbass. There's a reason your college science labs fork over hundreds of dollars for scales as opposed to buying a 20 dollar model from Wal-Mart and telling students to \"find your weight, then weigh yourself again with the specimen. Should be close enough...\"
The human body is funny and very difficult to correctly weigh. Weighing yourself precisely, 10 times in a row, will almost guaranteed give you 10 different results (whether off by 5lbs or .2lbs is immaterial). It simply is not an accurate measurement. Its good enough for what its made to do, but it isn't as accurate as all of you seem to think it is. If the OP weighed himself twice, once with the bag and once without, then I have no doubt in my mind that the result is flawed.
@Radi0logy: I think the point, next to the ridiculous amount of energy expended so far on the merits of bathroom scales, is that he claims to have been short-sold a product. You claim to have no-doubt that this company is ripping him off and proceeded to argue about measurement devices ad nauseum. I think that shaving the argument with Occam's Razor would suggest that a multinational company is probably not ripping off customers who can prove the deceit with a 2x4, a length of rope and a 10 lb. barbell weight. A more likely answer is that the contents of the bag melted at some point due to a bad freezer, improper storage or improper handling. He still was short-sold, but it probably wasn't intentional. Instead of spending the next three hours arguing why the DigiWeigh DW-68G has a 3 pound offset when you stand three inches from the edge, go buy a few more bags from different McDonalds and compare the weights. If you are going to talk like a scientist, stop arguing like a lawyer and start arguing like a scientist.
@ManiacalV: Not much effort on my part, I could do this all day.
But yes, I have honestly been considering buying a bag of ice and weighing it both ways to see what kind of margin of error there would be (I work so not exactly feasible the second the article was posted). However, I have nothing but a bathroom scale myself, so still turning over in my head how to get a more reliable weight on just the ice itself.
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@Radi0logy: 1) Weigh stuff for free at the post office.
2) You're still wrong about questioning the methodology.
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@HiPwr: Because most bathroom scales aren't accurate at low weights. In general, scales and balances as a whole are accurate over a range of weights that is about an order of magnitude. If your bathroom scale goes to 350lbs, it's probably accurate from 30-300 lbs. Anything outside that range and the scale won't be trustworthy.
What the OP did is precisely what to do when you need to weigh something that's too light to be weighed on your scale by itself, but larger than the margin of error for masses within the range of accuracy.
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@Radi0logy: \"I hardly think \"weighing yourself with and without the bag\" is a scientific way of obtaining the true weight\"
Why not?
@Eyebrows McGee (now with more baby!): @MaelstromRider: @jtheletter: @HiPwr: Many bathroom scales, especially digital ones, which I am guessing the OP is using by the exact weight power down when you step off. You usually tap them with your foot, where upon they turn on and \"tare\". You then step on when the 00.0 appears. Some show a \"animation\" when doing this, others stay blank until they tare. If you just step on, you will usually get an error. Now, since they tare each time, the difference in where you step on it affects the reading, as does how still you are, if you put your weight on the balls vs heel of your foot, how the subfloor underneath you spreads the weight, if there is more weight on one side of the scale vs the other, etc. Some scales will continue to take readings until they stabilize, and display that, much like a deli counter scale. Others, just \"pick\" a reading within xseconds of you stepping on, and display that w/no adjustment. Many bathroom scales will not display a weight under ~15lb as well, which is why you can not do small weights.
If you have ever used an analog scale, you see they will swing one way or another if you lean.
I have a $60 digital bathroom scale at home and a deli scale I found on the side of the road(a wire came loose inside, and the guy who was trying to fix it didn't have a set of security screw bits). If I want to do small precise, I use the deli scale, since it's a Hobart. To weight myself, I use the bathroom scale, and have stepped on it in different ways(left foot first vs right foot, leaning, etc) and have seen weight differences as much as 5 lb. in both directions.
Crying foul based on where you stand or your own personal scale's inaccuracy is not scientific either people. His method is sound and without knowing outside circumstances, assume the bag was light. Caveat: unless the bag never left freezing temperatures from it's origin to his scale, it's going to melt. Some minimum wager might have left them sitting outside the freezer while he mopped up the remains of the night managers dreams and aspirations. There's no way to tell if they short-sold him or if it just melted at some point without buying and testing samples from other shops and at other times.
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@Eyebrows McGee (now with more baby!): You really need to use an inertial balance in case of localized disturbances in the gravitational force (usually the result of psychokinetic levitation).
@Eyebrows McGee (now with more baby!): I found my scale will give me a different weight if I step on it several consecutive times, sometimes off by as much as 4.5 lbs.
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@AliyaBabasaur: That's the most inaccurate scale I've ever heard of. Why even have one at all? You'd be better off guessing your weight.
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@Scoobatz: Maybe he should procure the local crack cocaine dealer and inquire if he can borrow is Triple Beam scale. Those are pretty accurate I hear! :)
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@AliyaBabasaur: I liked the day I stepped onto my scale and it told me I lost 30lbs. Sadly, on my second attempt to verify I regained it.
@MaelstromRider: Nope, I don't. It was super cheap and it meets my needs as a person's body weight can easily fluctuate 5 or so pounds within a single day given food and fluid retention issues. I wouldn't, however, use it for scientific measurement.
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Maybe so, but if you step on a scale and it can't tell you the same thing twice, the scale doesn't work. It may give you a ball park figure, but that isn't something to be seen as very useful.
@ShadowFalls: Even the most precise scientific scales don't give you the same result twice - weighing things, especially humans, is not the exact science you seem to think it is.
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@AliyaBabasaur: If you willfully use an instrument that doesn't work, you can't really blame the method then, can you?
@AliyaBabasaur: Using a reliable scale works for Brad in his measurement, though. A person's body weight doesn't fluctuate 5 or so pounds within 30 seconds.
@Radi0logy: Actually, that's precisely the scientific method of weighing things as far as the procedure goes. First you weigh your sample container - in this case Brad - then you weight the sample and the container - brad holding ice - and subtract to get the sample weight.
How exactly do you think Brad's method altered the calculation? It's not as though holding a bag makes 3.8 lbs of stuff disappear, otherwise boy would backpacking be easy!
@jtheletter: No but how you position your feet on a scale cam affect the reading, Ie. a lot of scales read inaccurately if you stand on the sides of the scales, rather than in the center. That said I don't think for a minute, this is anywhere close to 10 pounds. But I used to work at a McD's and these kids don't have a scale or anything (we didn't even get guidelines on how many scoops of ice to put in.) I was always told to fill it until it \"had a lot of ice in it.\"
The problem is in the accuracy of the scale. The heavier Brad is, the more the weight of the ice gets lost in the margin of error. And those bathroom scales can be quite a bit inaccurate. I have a crappy digital one that can easily fluctuate a pound or two in either direction.
It would be better if he took several readings to see how precise his scale is.
@emnik: \"It would be better if he took several readings to see how precise his scale is.\"
I absolutely agree, however his calculation method is sound, which is what I was defending.
Although I'm still curious as to why he couldn't place a bag directly on the scale since it would fit and doesn't move around like pets.
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@trixrabbit: Yup. That's how you weigh pets... or anything that you'd have trouble keeping still on the scale.
What would be un-scientific about simple subtraction?
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If thats an actual picture...I don't even see how that could hold 10lbs, or if it could...I wouldn't want to drink water that dense o_0
@OminousG: I think the shape of the cubes may matter. IIRC, sometimes the ice cubes I got from fast food places was hollow in the center. Almost like a ring of ice. It's good for fountain soda, but when you goto bag, that empty space is a space where ice could be.
Just my thoughts.
@OminousG: maybe 10 pounds of water