I did QCE Chem and Phys so I understand the position you are in right now. Data tests usually consist of graphs or tables and identifying the relationship between two variables, using certain data points to find the value of a third variable etc. If your school library or any library has the Oxford Study Buddy for Chemistry and Physics, I highly suggest you get those - they saved my externals. If you cant find them, they’re usually $30 each.
For Physics, the data tests are usually based on different formulas. For Example, in a graph if you’re given how the current changes as the resistance changes across a circuit, you might be asked a) Find the voltage and b) Determine the mathematical relationship between the two.
Note: Always remember the mathematical relationship means the gradient. If you go to the QCAA website and look for the data tests there, it might be a better example.
For Chemistry, it’s very much based off experiments. There’s a few more explanations you need to give. For example, if it’s an equilibrium question, they’ll give you a graph and you’ll have to identify if it’s an endothermic or exothermic reaction, and give a sentence why. Other questions from this graph might be, that the concentration of the products were increased, how does it affect the equilibrium position, amount of reactants etc etc.
I hope this helped, and feel free to shoot more questions,