Hypothetical Research using the scientific method

Purpose:

I want to know if applying a rosemary hair mask for 30 days will it have any effects on hair growth.

I would select my male and female friends from several hair types (curly, straight, and wavy). Each one of my friends will use a rosemary hair mask treatment for one hour every night for 30 days. Their hair lengths will be measured until the end of the 30 days. All of my friends are given the exact same amount of product for their treatments. Half are given a rosemary hair mask and the others are given hair butter which has the same consistency as the rosemary hair mask but has no hair-growing benefits. No one will know what they are given because both hair masks have the same consistency, and color, and are fragranced with a rosemary scent. (the rosemary hair mask contains rosemary oil which promotes hair growth).

Hypothesis: If my friends apply the rosemary hair mask for 30 days, the length of their hair will increasingly grow.

Independent variable: Rosemary hair mask

Dependent Variable: Hair length

So my question is if I am providing a good example of the method and finish the questions below.

Who are your participants?

Is your study valid? Why or why not?

If not, how could you make it valid?

Is your study reliable? Why or why not?

If not, how could you make it reliable?

Is it a single blind or double blind study? Why or why not?

What findings will prove your hypothesis?

What findings will disprove your hypothesis?