Question

**HI6007 Statistics for Business Decisions**

**Tutorial 7 – Week 8**

**Question 1:**

The average starting salary of students who graduated from colleges of Business in 2009 was $48,400. A sample of 100 graduates of 2010 showed an average starting salary of $50,000. Assume the standard deviation of the population is known to be $8000. We want to determine whether or not there has been a significant increase in the starting salaries.

Step 1. Statement of the hypothesis

Step 2. Standardised test statistic formula

Step 3. State the level of significance

Step 4. Decision Rule (Draw a bell to show rejection zone)

Step 5. Calculation of the statistic

Step 6. Conclusion

**Question 2:**

Choo Choo Paper Company makes various types of paper products. One of their products is a 30 mils thick paper. In order to ensure that the thickness of the paper meets the 30 mils specification, random cuts of paper are selected and the thickness of each cut is measured. A sample of 256 cuts had a mean thickness of 30.3 mils with a standard deviation of 4 mils. At the .05 level of significance using the critical value approach, test to see if the mean thickness is significantly more than 30 mils.

**Question 3:**

Before the last presidential debates, 50% of registered votes indicated they were planning to vote for the incumbent president. In a recent poll of 1200 registered voters after the debates, 636 indicated they are planning to vote for the incumbent president. Has there been a significant increase in the proportion of registered voters who are planning to vote for the incumbent president?

- State the null and alternative hypotheses to be tested.
- Compute the test statistic.
- The null hypothesis is to be tested using
*α*= .05. Determine the critical value(s) for this test. - What do you conclude?

Answer #1

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