Problem with function

I made a formula in LibreOffice Writer with Insert > Object > Formula…

This is my source code:

{ sum from{i=1}to{8} (x_i - bar x )(y_i - bar y)} over
{ sqrt{sum from{i=1} to{8} (x_i - bar x)^2 }sqrt{sum from{i=1} to{8} (y_i - bar y)^2 } }

Did I do something wrong?

Please tell us the exact version of LibreOffice (Copy the text from Help > About) and the exact version of your operating system. You can edit your question to add this information.
I see the same wrong formula in Version:
Build ID: 32bdc5097013e7efd9c85e1b8df697880e66e925
CPU Threads: 4; OS Version: Windows 6.1; UI Render: default; Layout Engine: new;
TinderBox: Win-x86@62-merge-TDF, Branch:MASTER, Time: 2016-11-04_23:30:30
Locale: de-DE (de_DE); Calc: single

It looks good enough for me using LibreOffice in Danish locale.

image description

My suggestion is that you try to open the document on another computer or with another version of LibreOffice.