Question

Consumer Reports indicated that the average life of a refridgerator before replacement is mean= 14 years with a (95% of data) range from 9 to 19 years. Let x= age at which refrigerator is replaced. Assume that x has a distribution that is approximately normal.

a) Find a good approximation for the standard deviation of x values.

b) What is the probability that someone will keep a refrigerator fewer than 11 years before replacement?

c) What is the probability that someone will keep a refrigerator more than 18 years before replacement?

d) Inverse Normal Distribution: Assume that the average life of a refrigerator is 14 years, with the standard deviation given in part (a) before it breaks. Suppose that a company guarantees refrigerators and will replace a refrigerator that breaks while under guarantee with a new one. However, the company does not want to replace more than 5% of the refrigerators under guarantee. For how long should the guarantee be made (rounded to the nearest tenth of a year)?

The resting heart rate for an adult horse should average about (mean= 46 beats per minute) with a (95% of data) range from 22 to 70 beats per minute, based on information from the Merck Veterinary Manual. Let x be a random variable that represents the resting heart rate for an adult horse. Assume that x has a distribution that is approximately normal.

a) Estimate the standard deviation of the x distribution.

b) What is the probability that the heart rate is fewer than 25 beats per minute?

c) What is the probability that the heart rate is greater than 60 beats per minute?

d) What is the probability that the heart rate is between 25 and 60 beats per minute?

e) Inverse Normal Distribution A horse whose resting heart rate is in the upper 10% of the probability distribution of heart rates may have a secondary infection or illness that needs to be treated. What is the heart rate corresponding to the upper 10% cutoff point of the probability distribution?

Answer 1