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A friend of mine has a blender with 6 control selections: One off position, and five power settings in order of less to more power. Example below:

6 control options

A discussion has erupted over whether or not the middle power option (3) ought to represent:

A) 50% power (The middle is surely 50%):

enter image description here

B) 60% power (There are 6 positions if 0% is included, there is no middle position as such, and so assuming a linear scale):

enter image description here

While this isn't exactly a life and death situation, I would be interested in seeking more opinions. We are roughly split 50/50 on what it ought to be (yes, we could verify what it is by dismantling the blender and examining the circuity, but no one is interested in that minor detail) :)

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Who says that power increase is uniformly distributed over all the settings? –  Marjan Venema Jan 31 '13 at 7:27
    
Could you add a picture of what the dial looks like? Is the 3 in the middle or ofset to one side? –  icc97 Jan 31 '13 at 8:42
    
I'm afraid no picture is available, but I'm told the 3 is physically in the middle. –  scuzzy-delta Jan 31 '13 at 20:36
    
Thank you all for your comments and answers! –  scuzzy-delta Feb 3 '13 at 21:07
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4 Answers

up vote 9 down vote accepted

The percentage doesn't matter, what matters is what you do with each of the speed levels.

Was a person with proper knowledge of the tool (and its use cases) involved in discerning this enigma? Most of the times, these things have levels to please cooks and kitchen-passionate individuals who would know exactly what kind of outcome is achieved with every speed level of the blender; whether it's a chunky Salsa, or a Smoothie (as you can tell, for me blenders should have only an on/off button)

The right answer to your question is not going to be given by an engineer, or a casual user of the blender, but by a cook! :)

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+1 for bringing the perspective of the actual user into this! –  André Jan 31 '13 at 9:01
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This certainly depends on the blender but your first option seems wrong. The jumps in speed are not uniform. You get a huge boost from 3 to 4 and almost no difference from 4 to 5. Without dismantling the blender, I'd say you should be able to simply hear that that this is not the case!

What I expect is that the speed of the blade increments uniformly between power levels. So, each stop should follow on a quadratic curve in terms of power which would translate in a linear increase in rotational speed.

So, from a user-experience point-of-view, I would expect it to follow neither of your examples.

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In engineering terms, if it is linear it is 60%. If not, then nobody here knows.

If it started at 1 and not 0, then it would be 50%.

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Who says that power increase is uniformly distributed over all the settings? I added this comment to the question as well. It is an assumption that seems to have no ground? –  Marjan Venema Jan 31 '13 at 7:28
    
@MarjanVenema I said "if it is linear". If it's not, then there is no way of saying what it should be. –  JohnGB Jan 31 '13 at 13:43
    
Ah, missed those 4 words... Sorry –  Marjan Venema Jan 31 '13 at 13:45
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Good answer. The key phrase is 'If not, then nobody here knows.' For example, another possibility is a starting point of greater than 20% followed by a linear progression - this is based on the assumption that the blender at very low power is not capable of blending anything that people normally put in a blender. –  user1757436 Feb 1 '13 at 20:42
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From a user experience perspective, the key is to have a 'middle setting'. It doesn't really matter WHAT it is, specifically, but if your users like the idea of 'medium' then just make sure there is a medium setting...be it a number, letter or just a tick mark in the center.

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