Step 1 :A research institute poll asked respondents if they felt vulnerable to identity theft. In the poll, $n=949$ and $x=535$ who said 'yes'. Use a $90 \%$ confidence level.
Step 2 :The best point estimate of the population proportion $p$ is given by the formula $p = x/n$, where $x$ is the number of 'successes' (in this case, the number of people who said 'yes') and $n$ is the total number of trials (in this case, the total number of respondents).
Step 3 :In this case, $x = 535$ and $n = 949$. So, we can calculate $p$ by dividing 535 by 949.
Step 4 :The best point estimate of the population proportion $p$ is approximately 0.564. This means that approximately 56.4% of the respondents said 'yes' to feeling vulnerable to identity theft.
Step 5 :Final Answer: The best point estimate of the population proportion $p$ is $\boxed{0.564}$.