Question

Lifetimes of AAA batteries are approximately normally distributed. A manufacturer wants to estimate the standard deviation of the lifetime of the AAA batteries it produces. A random sample of 28 AAA batteries produced by this manufacturer lasted a mean of 9.1 hours with a standard deviation of 2.2 hours. Find a 95% confidence interval for the population standard deviation of the lifetimes of AAA batteries produced by the manufacturer. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.)

What is the lower limits of the 95% confidence interval?

What is the upper limit of the 95% confidence interval?

Answer #1

Lifetimes of AAA batteries are approximately normally
distributed. A manufacturer wants to estimate the standard
deviation of the lifetime of the AAA batteries it produces. A
random sample of
21
AAA batteries produced by this manufacturer lasted a mean of
11
hours with a standard deviation of
1.7
hours. Find a
95%
confidence interval for the population standard deviation of the
lifetimes of AAA batteries produced by the manufacturer. Then
complete the table below.
Carry your intermediate computations to at...

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 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 psychologist wants to estimate the standard deviation of IQ
scores. It is widely believed that IQ scores follow a normal
distribution. Her random sample of 25 IQ scores has a mean of 97.4
and a standard deviation of 17.2. Find the 99% confidence interval
for the population standard deviation based on this sample. Then
complete the table below. Carry your intermediate computations to
at least three decimal places. Round your answers to at least two
decimal places. (If necessary,...

A psychologist wants to estimate the standard deviation of IQ
scores. It is widely believed that IQ scores follow a normal
distribution. Her random sample of
25
IQ scores has a mean of
99
and a standard deviation of
13.2
. Find the
99%
confidence interval for the population standard deviation based
on this sample. Then complete the table below.
Carry your intermediate computations to at least three decimal
places. Round your answers to at least two decimal places. (If...

The scores on an examination in economics are approximately
normally distributed with mean 500 and an unknown standard
deviation. The following is a random sample of scores from this
examination. 422, 437, 472, 502, 534 Send data to Excel Find a 90%
confidence interval for the population standard deviation. Then
complete the table below. Carry your intermediate computations to
at least three decimal places. Round your answers to at least two
decimal places. (If necessary, consult a list of formulas.)...

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...

Suppose that the lifetimes of TV tubes are normally distributed
with a standard deviation of 1.1 years. Suppose also that exactly
40% of the tubes die before 5 years. Find the mean lifetime of TV
tubes. Carry your intermediate computations to at least four
decimal places. Round your answer to at least one decimal
place.

estion
The standard deviation of the daily demand for a product is an
important factor for inventory control for the product. Suppose
that a pharmacy wants to estimate the standard deviation of the
daily demand for a certain antibiotic. It is known that the daily
demand for this antibiotic follows an approximately normal
distribution. A random sample of
23
days has a sample mean of
125
orders for this antibiotic with a standard deviation of
10.1
orders. Find a
95%...

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