Question

The life span of a battery is normally distributed, with a mean of 2400 hours and a standard deviation of 50 hours. What percent of batteries have a life span that is more than 2460 hours? Would it be unusual for a battery to have a life span that is more than 2460 hours? Explain your reasoning.

What percent of batteries have a life span that is more than 2460 hours?

Approximately_______% of batteries have a life span that is more than 2460 hours.

Answer #1

The life spans of batteries are normally distributed, with a
mean of 2000 hours and a standard deviation of 30 hours.
a. How would we know by looking at the graph, if the probability
of batteries with a life span of less 1900 hours is more or less
than 50%> Explain your answer. DO NOT show any
mathematical work.
b. What percent of batteries have a life span that is more than
2065 hours? Show work as in class.

The life in hours of a battery is known to be approximately
normally distributed with standard deviation σ = 1.5 hours. A
random sample of 10 batteries has a mean life of ¯x = 50.5 hours.
You want to test H0 : µ = 50 versus Ha : µ 6= 50.
(a) Find the test statistic and P-value.
(b) Can we reject the null hypothesis at the level α = 0.05?
(c) Compute a two-sided 95% confidence interval for the...

The life of a fully-charged cell phone battery is normally
distributed with a mean of 14 hours with a standard deviation of 3
hours. What is the probability that 25 batteries last less than 16
hours?

The life of a fully-charged cell phone battery is normally
distributed with a mean of 14 hours with a standard deviation of 3
hours. What is the probability that 25 batteries last at least 13
hours?

The life of a fully-charged cell phone battery is normally
distributed with a mean of 14 hours with a standard deviation of 3
hours. What is the probability that 25 batteries last at least 13
hours?

A battery manufacturer finds that the life of its batteries are
normally distributed with a mean of 32 months and a standard
deviation of 5 months. Find the probability that a battery lasts
more than 36 months. Round off to four decimal places.

Suppose the life of a particular brand of calculator battery is
approximately normally distributed with a mean of 85 hours and a
standard deviation of 11 hours. Complete parts a through c.
a. What is the probability that a single battery randomly
selected from the population will have a life between 80
and 90 hours?
P(80≤ overbar x≤90)= (Round to four decimal places as
needed.)
b. What is the probability that 4 randomly sampled batteries
from the population will have...

Suppose the life of a particular brand of calculator battery is
approximately normally distributed with a mean of
80 hours and a standard deviation of 11 hours. Complete parts a
through c.
a. What is the probability that a single battery randomly selected
from the population will have a life between
and hours?
75
85
P(75 ≤ x ≤ 85) = (Round to four decimal places as needed.)
b. What is the probability that randomly sampled batteries from the
population...

The lifetime of a certain type of battery is normally
distributed with mean value 13 hours and standard deviation 1 hour.
There are nine batteries in a package. What lifetime value is such
that the total lifetime of all batteries in a package exceeds that
value for only 5% of all packages? (Round your answer to two
decimal places.)
hours

The lifetime of a certain type of battery is normally
distributed with mean value 11 hours and standard deviation 1 hour.
There are nine batteries in a package. What lifetime value is such
that the total lifetime of all batteries in a package exceeds that
value for only 5% of all packages? (Round your answer to two
decimal places.)
hours

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