# Confidence interval for proportion of Successes

I have the following histogram showing a dataset (1200 samples): Histogram

My goal with this, is to say that with a certain confidence, that 90% of all samples are within -0.25ms and +0.25ms. Since it's been a while since I've worked with statistics, I'd like some help.

How do I find that confidence level?

Best regards.

One possibility: Let $X$ be the number of Successes in $n = 2000,$ where a Success is an observation within $\pm 25ms.$ Also, let $P(\text{Success}) =\theta.$ Then $\hat \theta = X/n.$ A 90% confidence interval for $\theta$ is of the form $$\hat \theta \pm 1.645\sqrt{\frac{\hat \theta(1-\hat \theta)}{n}}.$$
Using this in a paper or report, you'd need to explain carefully because you have two intervals, $\pm 25$ms and and the confidence interval for $\theta.$