Study Lesson 8: Confidence Intervals for the Mean and Lesson 9: Hypothesis Testing for the Mean in my book, if you have it, to prepare for this topic. 

Important Note:  Unlike what I instruct in my book, make sure that you compute a P-value every single time that you perform a hypothesis test.  They have decided to not teach about critical values this term, so there is no need to use Table D to get z* or t*, the critical value, for any hypothesis test.  Because you are not using critical values, it therefore becomes essential to compute a P-value. 

Your steps to test a hypothesis should always be:

1. State the Hypotheses and so establish whether the test is upper-tailed, lower-tailed, or two-tailed.
2. State the given level of significance, alpha.  Let alpha = 5% if none is given.
3. Compute the test statistic using the correct formula for z or t.
4. Compute the P-value by marking the test statistic on a bell curve and shading the appropriate region according to your alternative hypothesis.
5. State your conclusion knowing that you always reject Ho if the P-value < alpha.

You will be using Table A and Table D while learning Lesson 8 and 9 and doing this assignment.  Here is a link where you can download those tables if you have not done so already:

1. Find the width of the interval (upper limit - lower limit) and divide by 2 to determine m, the margin of error.
2. We know that m = z* sigma/ square root of n, so figure out z*, algebraically.  Hint: z* = m times square root n divide by sigma.
3. Once you know z*, read Table D backwards to see what the confidence level is.  So, if you get z*=2.326, for example, then Table D tells us that you must be 98% confident.  (That is not the answer.)
   

To use JMP, click "New Data Table", then enter the data into Column 1.  Double-click Column 1 and name it Fill Pressure.  Now select "Analyze", "Distribution" and highlight Fill Pressure and click "Y, Columns", then click OK.  You are now looking at a histogram and stuff.

Click the red triangle next to Fill Pressure then select "Test Mean" from the drop-down list.  Enter in the mean from your null hypothesis (30)and enter in the given standard deviation (1.2). Click "OK" and JMP gives you the hypothesis test at the bottom of the printout.  Note that you cannot enter the level of significance they have given.  The level of significance is not relevant to JMP, you will use that yourself to make your decision.

Prob > |z| is the P-value for a two-tailed test.

Prob > z is the P-value for an upper-tailed test.

Prob < z is the P-value for a lower-tailed test.

Select the appropriate P-value from this list.

To make a confidence interval:

You aren't asked to make a confidence interval in this question, but why not do so to check your answer to part (a)?

Click the red triangle next to Fill Pressure then select "Confidence Interval" from the drop-down list.  Select "Other" to get a pop-up menu.  Type in the level of confidence you desire as a decimal.  For example, if you want a 97% confidence interval, type in 0.97.  (Here, you want a 95% confidence interval, so type 0.95, which is the default value anyway.)

Make sure you click the box saying "Use known Sigma".  Click "OK" and you will then get a pop-up menu to type in the sigma value given at the start of the problem (1.2, in this case).  Click "OK" and JMP gives you the Confidence Interval at the bottom of the printout.