Respuesta :
Answer:
65.54% probability that a battery lasts more than 4 hours
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 problem, we have that:
[tex]\mu = 260, \sigma = 50[/tex]
What is the probability that a battery lasts more than 4 hours?
4 hours is 4*60 = 240 minutes.
So this is 1 subtracted by the pvalue of Z when X = 240.
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{240 - 260}{50}[/tex]
[tex]Z = -0.4[/tex]
[tex]Z = -0.4[/tex] has a pvalue of 0.3446
1 - 0.3446 = 0.6554
65.54% probability that a battery lasts more than 4 hours
