I dont undersntand why my bell graph has negatives x values . Is it ok to have negative x-values ? What I have graph is the our data and narmalize column. Does this negative x values need to be fix in excel ? All I use from my data is the mean and standard deviation to creat the columns our data and normalize this is my data with increments of 10. I do not know if is normal to have negative values for x at the graph . Also what can I tell about the results of my graph about the data?

Mean 1.58

Std dev 1.16