Question

A random sample of 45 households was selected as part of a study on electricity usage., and the number of kilowatt-hours (kWh) was recoded for each household. The average usage was found to be 375 kWh. The population standard deviation is given as 51 KWh Assuming the usage is normally distributed, find the margin of error for a 99% confidence interval for the mean. [3 marks] 12.5 14.9 19.6 22.8

Answer #1

A random sample of 30 households was selected as part of a study
on electricity usage, and the number of kilowatt-hours (kWh) was
recorded for each household in the sample for the last quarter of
2010. The average usage was found to be 450 kWh. In a very large
study in the last quarter of the previous year, it was found that
the standard deviation of the usage was 81 kWh. Assuming that the
standard deviation is unchanged and that...

A random sample of 30 households was selected as part of a study
on electricity usage, and
the number of kilowatt-hours (kWh) was recorded for each household
in the sample for the
March quarter of 2006. The average usage was found to be 375kWh. In
a very large study in the
March quarter of the previous year it was found that the standard
deviation of the usage was
81kWh. Assuming the standard deviation is unchanged and that the
usage is...

The electric cooperative needs to know the mean household usage
of electricity by its non-commercial customers in kWh per day. They
would like the estimate to have a maximum error of 0.13 kWh. A
previous study found that for an average family the standard
deviation is 2.1 kWh and the mean is 15.8 kWh per day. If they are
using a 99% level of confidence, how large of a sample is required
to estimate the mean usage of electricity? Round...

The electric cooperative needs to know the mean household usage of
electricity by its non-commercial customers in kWh per day. They
would like the estimate to have a maximum error of 0.13 kWh. A
previous study found that for an average family the standard
deviation is 2.1 kWh and the mean is 15.8 kWh per day. If they are
using a 99% level of confidence, how large of a sample is required
to estimate the mean usage of electricity? Round...

Q-8 (1 of 1) The electric cooperative needs to know the mean
household usage of electricity by its non-commercial customers in
kWh per day. They would like the estimate to have a maximum error
of 0.14 kWh. A previous study found that for an average family the
standard deviation is 2.5 kWh and the mean is 17 kWh per day. If
they are using a 99% level of confidence, how large of a sample is
required to estimate the mean...

The electric cooperative needs to know the mean household usage
of electricity by its non-commercial customers in kWh per day. They
would like the estimate to have a maximum error of 0.09 kWh. A
previous study found that for an average family the standard
deviation is 2.1 kWh and the mean is 16.2 kWh per day. If they are
using a 99% level of confidence, how large of a sample is required
to estimate the mean usage of electricity? Round...

A random sample of 130 adult males was selected as part of a
study on weight loss. The average weight at the beginning of the
study was 265 pounds with a standard deviation of 22 pounds.
Assuming the weight is normally distributed, provide a 99%
confidence interval for the mean weight at the start of the study.
You MUST show your work to receive full credit.

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.

A random sample of 36 elderly cellphone users revealed that, in
a randomly selected month, they sent an average of 1200 text
messages. Assuming that the number of text messages sent by elderly
cellphone users in a month is normally distributed with a
population standard deviation of 100 text messages, determine the
following: • estimate, with 90% confidence, the true average number
of text messages sent by the elderly per month. • what is the
margin of error based on...

Problem 1 – Estimation of study hours
A random sample of 20 students drawn from a student population
in a very large public university. It is found that the 20 selected
students studied on average 16.4 hours per week outside class
contact time. Assume that study hours outside class contact time is
normally distributed. Also assume that the population standard
deviation on study hours outside class contact time is 5.5 hours
per week. Construct a 98 percent confidence interval for...

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