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ENGR/PHYS 216 Homework Assignment #5 Introduction to Statistics. Confidence Intervals This is an individual assignment. There are five (5) problems to solve. Please, submit the following item(s) to the appropriate eCampus Submission Box: 1. A scanned/photographed copy of your hand-written solutions to the problems; file name Homework5.pdf. make sure to include Given, Find, etc. No diagrams = no credit. Problem 1. For a normal population with known variance $\sigma^2$, what is the confidence level for the CI $\bar{x} - 2.14\sigma/\sqrt{n} \le \mu \le \bar{x} + 2.14\sigma/\sqrt{n}$? Problem 2. An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. Problem 3. You are working part-time at a road construction firm. Your boss knows you are learning some statistics in your classes this semester and calls you into the office. He says, "We've taken sample densities from loads of asphalt we've gotten from our supplier. The information from their company says their process produces a consistent density with a standard deviation of 2.65 pounds per cubic foot. Here's the data we've collected. Can you give me an estimate of the

          ENGR/PHYS 216
Homework Assignment #5
Introduction to Statistics. Confidence Intervals
This is an individual assignment. There are five (5) problems to solve. Please, submit the
following item(s) to the appropriate eCampus Submission Box:
1. A scanned/photographed copy of your hand-written solutions to the problems; file name
Homework5.pdf. make sure to include Given, Find, etc. No diagrams = no credit.
Problem 1.
For a normal population with known variance $\sigma^2$, what is the confidence level for the CI
$\bar{x} - 2.14\sigma/\sqrt{n} \le \mu \le \bar{x} + 2.14\sigma/\sqrt{n}$?
Problem 2.
An electrical firm manufactures light bulbs that have a length of life that is approximately normally
distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780
hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm.
Problem 3.
You are working part-time at a road construction firm. Your boss knows you are learning some
statistics in your classes this semester and calls you into the office. He says, "We've taken sample
densities from loads of asphalt we've gotten from our supplier. The information from their company
says their process produces a consistent density with a standard deviation of 2.65 pounds per cubic
foot. Here's the data we've collected. Can you give me an estimate of the

ENGR/PHYS 216
Homework Assignment #5
Introduction to Statistics. Confidence Intervals
This is an individual assignment. There are five (5) problems to solve. Please, submit the
following item(s) to the appropriate eCampus Submission Box:
1. A scanned/photographed copy of your hand-written solutions to the problems; file name
Homework5.pdf. make sure to include Given, Find, etc. No diagrams = no credit.
Problem 1.
For a normal population with known variance σ^2, what is the confidence level for the CI
x̅ - 2.14σ/√(n)≤μ≤x̅ + 2.14σ/√(n)?
Problem 2.
An electrical firm manufactures light bulbs that have a length of life that is approximately normally
distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780
hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm.
Problem 3.
You are working part-time at a road construction firm. Your boss knows you are learning some
statistics in your classes this semester and calls you into the office. He says, "We've taken sample
densities from loads of asphalt we've gotten from our supplier. The information from their company
says their process produces a consistent density with a standard deviation of 2.65 pounds per cubic
foot. Here's the data we've collected. Can you give me an estimate of the

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