First thing first. This question is related to hypothesis of variance .We will use chi square test to verify this claim
Ha: Vo < (0.2)2
H0: V0>= (0.2)2
. Its a left side test .at 0.005(.5%) significance level with 29 Degree of Freedom(we will look for value corresponding to 99.5% against 29 , the critical value is around 15
our test Stats is = (n-1) x S2 / V02 = 29 x .12x.12/(0.2 x0.2)= 10.44. our test stats is below critical level .so we will reject the null and accept that SD is less than 0.2