Answer:
Positive statements are statements that describe things as they are, based on empirical evidence. Normative statements describe whether something is good or bad, desirable or undesirable. They can be recommendatios or opinions, or both at the same time.
1. Teenagers shouldn't be permitted to buy cigarettes - Normative statement. It finds teenage smoking as undesirable.
2. Nuclear energy is cleaner than coal and oil based energy - Postive statement. It is describing a fact, not explicitely saying whether nuclear energy is better or not (even if implicitily it might be saying so).
3. We need more police on inner dash city streets - Normative statement. This statement is finding that more police is desirable.
4. Netflix original programming is better than network TV shows - Normative statement. It is giving an opinion, but it's still a positive statement.