Question

1. Nine samples of PVC pipe of equal wall thickness are tested under three temperature conditions to failure, yielding the results shown below. Research questions: Is mean burst strength affected by temperature level? Is there an “ideal” temperature level? Explain. You will need to enter the data into Minitab.

Burst Strength of PVC Pipes (Pounds Per Square Inch)
Temperature
Hot (70 Degrees C)	Warm (40 Degrees C)	Cool (10 Degrees C)
250	321	358
301	342	375
235	302	328
273	322	363
285	322	355
260	315	336
281	299	341
275	339	354
279	301	342

• At the 0.05 level of significance, determine if there is a difference mean burst strength by temperature level. State your hypotheses and show all 7 steps clearly.
• Use Levene’s test to determine if the assumption of homogeneity of variances is valid. Give the hypotheses, test statistic, p-value, decision and conclusion. Use the 0.05 level of significance.  
• Verify with Minitab by attaching or including relevant output.

Please show your steps on Mini Tab

Answer 1

a) To test if there is a difference mean burst strength by temperature level,

Using Minitab, (Stat -> ANOVA -> One Way), we get the following output -

Here,

The value of test statistic F = 50.18

and P-value = 0

Since P-value < 0.05, so at 5% level of significance, we reject the null hypothesis.

Conclusion: We can conclude that there is significant difference mean burst strength by temperature level.

b) To test  if the assumption of homogeneity of variances is valid,

Using Minitab, (Stat -> ANOVA -> Test for Equal Variances), we get the following output -

Here, for Levene’s test

The value of test statistic = 0.15

and P-value = 0.858

Since P-value > 0.05, so at 5% level of significance, we fail to reject the null hypothesis.

Conclusion: We can conclude that there is no significant difference among variances by temperature level.