In October of 2012, Apple introduced a much smaller variant of the Apple iPad, k

Question

In October of 2012, Apple introduced a much smaller variant of the Apple iPad, known at the iPad Mini. Weighing less than 11 ounces, it was about 50% lighter than the standard iPad. Battery tests for the iPad Mini showed a mean life of 10.25 hours (The Wall Street Journal, October 31, 2012). Assume that battery life of the iPad Mini is uniformly distributed between 8.5 and 12 hours.

a. What is the probability that the battery life for an iPad Mini will be 10 hours or less (to 4 decimals)?

b. What is the probability that the battery life for an iPad Mini will be at least 11 hours (to 4 decimals)?

c. What is the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours (to 4 decimals)?

d. In a shipment of 100 iPad Minis, how many should have a battery life of at least 9 hours (to nearest whole value)?

Explanation / Answer

What is the probability that the battery life for an iPad Mini will be 10 hours or less (to 4 decimals)?

Ans: (10-8.5)/3.5 = 1.5/3.5 = 0.4286

What is the probability that the battery life for an iPad Mini will be at least 11 hours (to 4 decimals)?

Ans: (12-11)/3.5 = 1/3.5 = 0.2857

What is the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours (to 4 decimals)?

Ans: (11.5-9.5)/3.5 = 2/3.5 = 0.5714
. In a shipment of 100 iPad Minis, how many should have a battery life of at least 9 hours (to nearest whole value)?

Ans: 100*(12-9)/3.5 = 100*3/3.5 = 86

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