(a) Hong Kong Government is promoting the use of energy efficient home appliances, including light bulbs. According to results of a concern group, the life-time of a particular brand of energy saving light bulb is found to be normally-distributed with mean life time of 5864 hours and standard deviation of 328 hours.
(i) Find the value of t hours such that 95% of such light bulbs can last longer than t hours. (5 marks)
(b) The production of energy saving light bulbs requires quality control process. Each light bulb is inspected before being shipped to the market. On average, 10% of such light bulbs produced are defective and 10% of such light bulbs are misclassified in the quality control process.
(i) Present the above information with a tree diagram. (3 marks)
- 知足常樂Lv 77 年前最愛解答
2013-12-11 19:25:06 補充：
-(1.60 + 0.04) = -1.64
睇 -1.64 對應表中的 .0505 代表 standard normal -1.64 以左的 area/proportion/probability 是 5.05%
睇 -1.65 對應表中的 .0495 代表 standard normal -1.65 以左的 area/proportion/probability 是 4.95%
2013-12-11 19:25:17 補充：
如果問那個quantile可使standard normal 以左的 area/proportion/probability 是 5% (即以右的是 95% ), 那從上述資料可以推出是 -1.645
-1.64 5.05% 94.95%
-1.65 4.95% 95.05%
-1.645 5% 95%