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

Step 2. Standardised test statistic formula

Step 3. Level of significance

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

Step 5. Calculation of the statistic

Step 6. Conclusion