Samples Production Package

A machine used for packaging seedless golden raisins is set so that ther standard deviation in the weight of raisins packged per box is 0.25 ounce. The operations manager wishes to test the machine setting and selects a sample of 30 consecutive raisin packges filled during the production process. Their weights are as recorded below
Weight
15.2
15
14.3
15.3
15.2
14.4
15.1
15.4
15.5
15.7
15.6
15.4
15.3
15.7
15.2
15
15.4
15.5
15.1
15.3
15.6
14.3
14.9
15.1
14.6
14.8
15.3
14.5
14.6
15.1
a. At the 0.05 level of significance, is there evidence that the population standard deviation differs from 0.25 ounces?
b. What assumptions are made in order to perform this test?
c. What are the degrees of freedom?
d) What is the chi-statistic?
This is all the info I have