Finding acceleration from graphs (s vs t^2)

This is a bit of a physics question but I think you guys would know it, it's for a lab, anyways:

If I’m to graph a plot of s (displacement) vs t^2 (time squared) then what would be the independent and dependent variable, t or s? I’m supposed to supposed to use this graph to find a slope with error bars and use the appropriate kinematics equation [which I think is s(t) = 1/2 at^2 (the vi*t is 0)]. The slope I will attain from the t^2 versus s graph, what will it represent? And how could I possibly plug it back into the equation to find acceleration? Thanks.

Also when I graph my results, should it be a positive or negative slope if the distance and time are decreasing every time? Because if it's a negative slope than that would mean that the x values for time squared would decrease going from 9.826 to 7.132

This is the table I'll use

Average Displacement (cm)---------->Average Time squared (t²) s

Distance 1 152.90 ± 0.05 cm--------->9.686

Distance 2 143.66 ± 0.05 cm--------->9.321

Distance 3 133.30 ± 0.04 cm--------->8.588

Distance 4 123.56 ± 0.02 cm--------->7.896

Distance 5 113.76 ± 0.02 cm--------->7.132