[In short, any of the two quantities will satisfy your need- $d$ (easy to calculate), or a monotonic function of $d$ $P(D\lt d)$ (needs bootstrapping to calculate). Both share the property that smaller they are, bigger the chance that new point comes from surveyed data. are described below. For a detailed discussion, read on.]
The problem can essentially be reformulated as a statistical hypothesis testing problem, and we need to test if the new observation comes from the surveyed population.
I will outline the construction of one such test. For this I will assume the questions are independent.
$H_0$: New observation comes from the population. Assuming independence, the population can be characterized by a vector of probabilities $(p_1,p_2,...,p_n)$ for the $n$ questions. These $p_i$'s correspond to your calculated % of "yes".
$H_1$: New observation does not come from the population.
Suppose the new observation is $B=(B_1,...,B_n)$, where each $B_i$ is 1 if "yes" and 0 if "no" was entered.
A reasonable test statistic would be $D=\sum (B_i-p_i)^2$, which looks at the total squared deviation from the expected answers.
You can then judge if you want to label the new sample as coming from your population by evaluating $P(D\lt d)$ - if this probability is <5%, you can say with 95% confidence that it comes from the sample.
Computing the exact distribution of $D$ under $H_0$ will be challenging, to determine $P(D\lt d)$ you can use bootstrapping - i.e. simulating observations under $H_0$ a million times and checking what proportion of times your simulated $D$ is less than observed $d$.
If you need a 0 to 1 valued 'correlation' like statistic, you can look at $1-P(D\lt d)$.