experiment times: .15, .13, .16, .14, .15, .14, .15, .14

so i found the average to be .15
and the highest value was .16
the lowest value was .13

so what is the uncertainty? (in other words... .15 plus or minus what number?) please explain. thanks

On my trusty TI30 calculator, I ran the data as

n=8, sigma(n-1)=.009258, mean=.145

So I don't know how you got your "average"

Three standard deviations would be +-.028

I have no idea what you have defined uncertainity as, three standard deviations is usually plenty.