I'd like to make a frame (probably using mdframed) as in the example picture I included. I looked around on this website and tried to google the think, but I don't even know how to desrcibe this in words (when I type "header" or "text inside frame" I get very different results. Sorry, I'm not a native speaker).
The example is taken from a slide of a statistics course I attended a while ago. Unfortunately, I don't have the LaTeX-file, only the finished PDF document. Would be great if anyone could give me a hint how to do this in LaTeX. Thanks!