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I was thinking 32.5%. Due to 70% of the 25% who do own a device would be 17.5% and then minus that from the 50%.

But the only answers are- 50%, 43%, 37.5%, 60% or Cannot Say.

Am i missing something really obvious here?

Ross Millikan
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screencut
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  • Does the 70% mean 70% of all users that own a device or 70% of the users that don't mind an algorithm learning their behaviors? – John Douma Apr 20 '18 at 22:45
  • I imagine it is 70% of users that own a device don't mind an algorithm learning their behaviours – screencut Apr 20 '18 at 22:48

2 Answers2

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Out of $100$ respondents there are $25$ that own a zero UI device, $17.5$ of whom are uncomfortable. There are a total of $50$ that are uncomfortable, so there are $32.5$ that are uncomfortable and do not own a zero UI device out of $75$ that do not own a zero UI device. This is $\frac {32.5}{75}=43\frac 13\%$ but your test writer's calculator seems not to do decimals and produced $43\%$.

Ross Millikan
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Let say T is the total users, x is zero ui users, and y the non zero ui users. So we get $T = x + y$ and $T = 4x$ and $y = 3x$.

Next we know that 50% overall users were confident, and 70% of zero ui users were confident. This translates to $.5T = .7x + py$. Using the substitutions above we get $.5(4x) = .7x + p(3x)$
$$ 2x = .7x + 3px \\ 2x = x(.7 + 3p) \\ 2 = .7 + 3p \\ 1.3 = 3p \\ p = \frac{13}3 \approx 43.3 \% $$

Shah.S
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