premise: How to smooth frizzy hair<br>Wash with a moisturizing shampoo. Frizz is often caused by dryness, so it's important to restore moisture to your hair in the shower. Always use a sulfate-free shampoo.
hypothesis: Frizz is not caused by dryness 100% of the time, or in all cases.
reason: With the context saying "Frizz is often caused by dryness," this implies that dryness does not do so every single time / 100% of the time.