How to calculate number 8 using calculator. I need help ASAP. the answer for num

Question

How to calculate number 8 using calculator. I need help ASAP. the answer for number 8 is D)2.5%

Use the following density curve to answer questions 7 and 8: Many residents of suburban neighborhoods own more than one car but consider one of their cars to be the main family vehicle. The age of these family vehicles can be modeled by a normal distribution with mean 2 years and standard deviation 6 months. 7. Wha t percentage of family vehicles is between 1 and 3 years old? A) Cannot be determined based on the information given B) 68% C) 95% D) 99.7% 8. What percentage of family vehicles is more than 3 years old? A) 47.5% B) 34% C) 95% D) 2.5%

Explanation / Answer

Here we need to use 68-95-99.7 rule which says that:

68% of the data lies within 1 SD of the mean.

95% of the data lies within 2 SD of the mean.

99.7% of the data lies within 3 SD of the mean.

Hence,

8. P(X > 3)

= P(z > (3 - 2)/0.5)

= P(z > 2)

= 5% /2 [Because 95% data lies within 2 SD so 2.5% area will be of each side of z = -2 and z = 2]

= 2.5%

Option D is correct.

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