The materials I will need are: Assorted masses, several springs of different lengths, a meter stick, and a stand to hang the spring from.

To set up the experiment, I will clamp the stand to the edge of the table, and I will hang a spring from it, which I will hang a mass from. Then, I will hang the mass, and lift it up about 0.2 meters less than where it would normally stretch with the mass on the end. Then, I will let go and record how long a period is when the mass "bounces" after I let go of it. I will also measure the masses to make sure I know how big they are.

The physical quantities I will measure are:
Period
Mass

The instruments I will use to measure my physical quantities are:
A stopwatch
A metric scale

To measure the physical quantities, I will first place the mass on the metric scale, where I can see how big it is exactly. Afterwards, When I hang the mass from the spring and "bounce" it, I will time how long it takes for the mass to go up and down, or one period.

Each measurement of the period will be taken three times and averaged together, to attempt to offset human error, and to get the correct data.

To test the validity of this hypothesis, each different mass will be tested in the exact same way by measuring the period of its motion with the stopwatch on the same spring.

With the data I collected from the experiment described in the question before this, I will compare the (averaged) periods of each different mass with one another, and if there is any major variation, then I will know that this thesis is invalid.

y = 2.5x^2 + 0.5x - 7E-15

Mass=2.5Period^2 + 0.5Period-7E-15

Polynomial

When one increases, so does the other, although not equally.

The Period increases as well.