SOLUTION: A mobile phone company finds the lifespan for one brand of its mobile phones is normally distributed with a mean of 48,400 hours (approx. 5.5 years) and a standard deviation of 500

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Question 1185533: A mobile phone company finds the lifespan for one brand of its mobile phones is normally distributed with a mean of 48,400 hours (approx. 5.5 years) and a standard deviation of 5000 hours.


Answer the following:
If the manufacturer is willing to replace no more than 10% of the mobile phones, what should be the approximate number of hours for a warranty? Note: Express your answer in whole number.
What is the probability that a mobile phone will last between 36,400 hours and 44,400 hours? Note: Express your answer in four decimal places.
What is the probability that a mobile phone will last at least 55,900 hours? Note: Express your answer in four decimal places.
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
the calculator at https://davidmlane.com/hyperstat/z_table.html can help you find the answer to this.

mean = 48400
standard deviation = 5000

question 1:

If the manufacturer is willing to replace no more than 10% of the mobile phones, what should be the approximate number of hours for a warranty? Note: Express your answer in whole number.

the warranty should state that the approximate number of hours of life for the phone is guaranteed to be at least 41992.242

round to units to get 41992.

here are the results from the calculator.


question 2:

What is the probability that a mobile phone will last between 36,400 hours and 44,400 hours? Note: Express your answer in four decimal places.

the probability is equal to .2037

here are the results from the calculator.



question 3:

What is the probability that a mobile phone will last at least 55,900 hours? Note: Express your answer in four decimal places.

the probability is equal to .0668

here are the results from the calculator.



in question 1, you were looking for a value from an area.

in question 2 and 3, you were looking for an area from a value.

i confirmed with that the answers were consistent with the answers from my ti-84 plus scientific calculator.