Question 6 (7 marks)

For a particular range of cosmetics a filling process is set to fill tubs of face powder with 4 grams on average and standard deviation of 1 gram. A quality inspector takes a random sample of nine tubs and weighs the powder in each. The average weight of powder is 4.6 grams. What can be said about the filling process, with 95% level of confidence?

Step 1. Statement of the hypotheses (1 mark)

Step 2. Standardised test statistic formula (1 mark)

Step 3. Level of significance (0.5 mark)

Step 4. Decision Rule (Draw a bell to show rejection zone) (2 marks)

Step 5. Calculation of the statistic (1.5 marks)

Step 6. Conclusion (1 mark)