how to calculate Ic as the current through the collector and function of the transistor
They just mean that different transistors have different values of beta.

Since it's a beginners tutorial they're glossing over the fact that even for a given transistor, beta will vary depending on temperature, bias point, etc.


  I haven't really been able to look at the data sheet and figure out where that information is.


Some data sheets will use the symbol hfe instead of \$\beta\$.

Usually the temperature dependence will be given only as a typical curve, not a minimum/maximum specification. Even the nominal beta spec range will usually be quite broad,  pften with ratios in the neighborhood of 5:1 between maximum and minimum. 

What this means is you need to design your circuit (usually by including feedback) so that the overall behavior of the circuit is insensitive to the beta of the individual transistors.