Question

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, 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

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...

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 union for a particular industry has determined that the
standard deviation of the daily wages of its workers is $
19
. A random sample of
150
workers in this industry has a mean daily wage of $
112
. Find a
99%
confidence interval for the true mean daily wage of all union
workers in the industry. Then complete the table below.
Carry your intermediate computations to at least three decimal
places. Round your answers to one decimal...

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...

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%...

A researcher wishes to estimate the proportion of x-rays
machines that malfunction. A random sample of 275 machines is
taken, and 88 of the machines in the sample malfunction. Based upon
this, compute a 95% confidence interval for the proportion of all
x-ray machines that malfunction. Then complete the table below.
Carry your intermediate computations to at least three decimal
places. Round your answers to two decimal places. ( If necessary,
consult a list of formulas.)
What is the lower...

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...

Scores on an IQ test are normally distributed. A sample of 5 IQ
scores had standard deviation s=8. (a) Construct a 90% confidence
interval for the population standard deviation . Round the answers
to at least two decimal places. (b) The developer of the test
claims that the population standard deviation is 15. Does this
confidence interval contradict this claim? Explain.

IQ scores among the general population have a mean of
100
and a standard deviation of
15
. A researcher claims that the standard deviation,
σ
, of IQ scores for males is less than
15
. A random sample of
16
IQ scores for males had a mean of
98
and a standard deviation of
10
. Assuming that IQ scores for males are approximately normally
distributed, is there significant evidence (at the
0.1
level of significance) to conclude...

Problem Page Suppose that IQ scores in one region are normally
distributed with a standard deviation of 15 . Suppose also that
exactly 60% of the individuals from this region have IQ scores of
greater than 100 (and that 40% do not). What is the mean IQ score
for this region? Carry your intermediate computations to at least
four decimal places. Round your answer to at least one decimal
place.

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