Instruction: Answer ALL Questions. Students are required to copy the questions.

1. From a random sample of 100 students who have passed a statistics course, the average score was 71.8. Assuming that the population standard deviation is 8.9, with a significance level of 0.05, does it seem to signify that the average score is more than 70? (10 marks)

2. A flour mill produces flour in small bags before distributing them to wholesalers. The average weight of each bag is 8 kg with a standard deviation of 0.5 kg. A random sample of 50 bags was taken and found that the average weight is 7.8 kg. Using a significance level of 0.01, test the hypothesis that = 8 against the alternative where 8 (10 marks)

3. It is claimed that a car is driven on the average more than 20 000 kilometres per year. To test this claim, a random sample of 30 car owners has been selected. The owners were asked to keep record of the kilometres they travel. Would you agree with this claim if the random sample showed an average of 22 500 kilometres and a standard deviation of 5 500 kilometres? Use a 0.05 level of significance to justify your answer. (10 marks)

4. Tenaga Nasional Berhad (TNB) has listed a variety of home appliances each with annual total electricity consumption in kilowatt-hours. For a medium -sized refrigerator, the annual electricity consumptin is said to be an average of 46 kilowatt-hours. A random sample of 12 homes included in the study showed that medium -sized refrigerators consume the electricity at an average of 42 kilowatt-hours per year with a standard deviation of 11.9 kilowatt-hours. At a significance level of 0.05 and assuming that the population is normal, does this sample show that medium -sized refrigerators consume, on the average, less than 46 kilowatt-hours per year? (10 marks)