Question

A company has developed a new type of lightbulb, and wants to estimate its mean lifetime. A simple random sample of 81 bulbs had a mean lifetime of 585.6 hours with a standard deviation of 28 hours.

a. Calculate the standard error and round your answer to 1 decimal place: ________________

b. Use StatCrunch to find a 95% confidence interval: _______________________

c. Interpret what your confidence interval means in the context of this problem.

d. If the company was hoping that the population mean was 600 hours, is that likely based on your confidence interval?

Answer #1

A company has developed a new type of light bulb, and wants to
estimate its mean lifetime. A simple random sample of 12 bulbs had
a sample mean lifetime of 739 hours with a sample standard
deviation of 45 hours. It is reasonable to believe that the
population is approximately normal. Find the lower bound of the 95%
confidence interval for the population mean lifetime of all bulbs
manufactured by this new process
Round to the nearest integer Write only...

A company wants to know the useful life of a new revolutionary
lightbulb it has just developed. A mean of 64 of these bulbs
revealed a mean useful life of 30,000 with a standard deviation of
1,500 hours.
Use this information to develop a 95% confidence interval for
the mean useful life of all new revolutionary lightbulbs.
Use this information to develop a 98% confidence interval for
the mean useful life of all new revolutionary lightbulbs.

9. The standard deviation of the lifetime of a certain type of
lightbulb is known to equal 100 hours. A sample of 169 such bulbs
had an average life of 1350 hours. Find a
(a) 90percent (b) 95percent (c) 99percent
confidence interval estimate of the mean life of this type of
bulb.

*Please Answer All *
1. A company has developed a new type of light bulb and wants to
estimate its mean lifetime. A simple random sample of 12 bulbs had
a sample mean lifetime of 651 hours with a sample standard
deviation of 31 hours. It is reasonable to believe that the
population is approximately normal. Find the lower bound of the 95%
confidence interval for the population mean lifetime of all bulbs
manufactured by this new process. Round to...

A light bulb manufacturer wants to compare the mean lifetimes of
two of its light bulbs, model A and model B. Independent random
samples of the two models were taken. Analysis of 11 bulbs of model
A showed a mean lifetime of 1361hours and a standard deviation of
83 hours. Analysis of 15 bulbs of model B showed a mean lifetime of
1304 hours and a standard deviation of 81hours. Assume that the
populations of lifetimes for each model are...

The lifetime of a certain brand of electric light bulb is known
to have a standard deviation of 53 hours. Suppose that a random
sample of 100 bulbs of this brand has a mean lifetime of 481 hours.
Find a 99% confidence interval for the true mean lifetime of all
light bulbs of this brand. Then complete the table below. Carry
your intermediate computations to at least three decimal places.
Round your answers to one decimal place. (If necessary, consult...

The lifetime of a certain brand of electric light bulb is known
to have a standard deviation of
51
hours. Suppose that a random sample of
150
bulbs of this brand has a mean lifetime of
481
hours. Find a
90%
confidence interval for the true mean lifetime of all light
bulbs of this brand. Then complete the table below.
Carry your intermediate computations to at least three decimal
places. Round your answers to one decimal place. (If necessary,
consult...

Company A claims that its light bulbs are
superior to those from company B. A study shows
that a sample of 40 bulbs from company A has a
mean lifetime 647 hours of continuous use with a standard deviation
of 27 hours, while a sample of 40 bulbs from company
B had a mean life time of 638 hours of continuous use with
a standard deviation of 31 hours. Calculate the 83% confidence
interval for the difference of the two...

The lifetime of a certain type of battery is known to be
normally distributed with a population standard deviation of 20
hours. A sample of 50 batteries had a mean lifetime of 120.1
hours.
a. What is the point estimate?
b. Calculate the sampling error.
c. Construct a 95% confidence interval for the population mean.
Explain the answer in a sentence.

A
simple random sample of electronic components will be selected to
test for the mean lifetime in hours. Assume that component
lifetimes are normally distributed with population standard
deviation of 31 hours. How many components must be sampled so that
a 99% confidence interval will have margin of error of 6 hours?
Write only an integer as your answer.

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