Question

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 a list of formulas.) What is the lower limit of the 99% confidence interval? What is the upper limit of the 99% confidence interval?

Answer #1

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...

The lifetime of a certain brand of battery is known to have a
standard deviation of 16 hours. Suppose that a random sample of 50
such batteries has a mean lifetime of 37.6 hours. Based on this
sample, find a 90% confidence interval for the true mean lifetime
of all batteries 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...

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...

Let X denote the lifetime of a light bulb of a certain brand.
Suppose that the lifetime of a light bulb of this particular brand
has an exponential distribution with mean lifetime of 200 hours.
What is the probability that a light bulb has a lifetime between
100 and 400 hours?

It is known that the lifetime of a certain type of light bulb is
normally distributed with
a mean lifetime of 1,060 hours and a standard deviation of 125
hours. What is the
probability that a randomly selected light bulb will last
between 1,000 and 1,100 hours?

A technician in a light bulb manufacturing plant desires
to determine the mean lifetime of the light bulbs in the most
recent production run. The technician takes an SRS of 20 light
bulbs. The mean and standard deviation of this sample is 72 hours
and 15 hours respectively.
What is the 99% confidence interval for the mean
lifetime ( ยต ) for all light bulbs in this production
run?

Suppose that for a particular brand of
light bulb, the lifetime (in months) of any randomly selected bulb
follows an exponential distribution, with parameter l = 0.12
a) What are the mean and standard deviation for
the average lifetime of the particular brand of light bulbs? What
is the probability a single bulb will last greater than 9
months?
b)
If we randomly select 25 light bulbs of the particular
brand, what are the mean and standard...

In a sample of 80 light bulbs, the mean lifetime was 1217 hours
with a standard deviation of 53 hours.
Find a 90% upper confidence interval for the mean lifetime.
(Round the final answer to two decimal places.)
The 90% upper confidence bound is ____
I got 1226.75, but it says it incorrect.

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.

Suppose that a certain brand of light bulb has a mean life of
450 hours and a standard deviation of 73 hours. Assuming the data
are bell-shaped: (Show work to get full credit)
a. Would it be unusual for a light bulb to have a life span of
320 hours? 615 hours? Justify each response.
b. According to the Empirical Rule, 99.7% of the light bulbs
have a lifetime between what two values?
c. Determine the percentage of light bulbs...

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