Respuesta :
Answer:
The company will expect to replace 13.03% of batteries.
The company should guarantee the batteries for 35 months.
Step-by-step explanation:
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this question, we have that:
[tex]\mu = 45, \sigma = 8[/tex]
If Quick start guarantees a full refund on any battery that fails within the 36 month period after purchase, what percentage of its batteries will the company expect to replace?
This is the pvalue of Z when X = 36. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{36 - 45}{8}[/tex]
[tex]Z = -1.125[/tex]
[tex]Z = -1.125[/tex] has a pvalue of 0.1303.
The company will expect to replace 13.03% of batteries.
If quick Start does not want to make refunds for more than 10% ofits batteries under the full refund guarantee policy, for how longshould the company guarantee the batteries
They should guarantee to the 10th percentile, which is X when Z has a pvalue of 0.1. So it is X when Z = -1.28.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]-1.28 = \frac{X - 45}{8}[/tex]
[tex]X - 45 = -1.28*8[/tex]
[tex]X = 34.76[/tex]
Rounding to the nearest month
The company should guarantee the batteries for 35 months.
