# MATH 221 Week 6 DQ Confidence Interval Concepts

**This file of MATH 221 Week 6 DQ Confidence Interval Concepts comprises:**

1. Find the margin of error for the given values of c = 0.95 , s= 3.6 and n= 36

(Round to three decimal places as needed)

STUDY PLAN: 6.1.13, 6.1.15

OBJECTIVE: CONSTRUCT AND INTERPRET CONFIDENCE INTERVALS FOR THE POPULATION MEAN

2. You are given the sample mean and the sample standard deviation. Use this information to construct the 90% and 95% confidence intervals for the population mean. Which interval is wider? If convenient, use technology to construct the confidence intervals.

A random sample of 37 gas grills has a mean price of $637.70 and a standard deviation of $58.30

(Round to one decimal place as needed)

STUDY PLAN: 6.1.35, 6.1.36, 6.1.37, 6.1.40

OBJECTIVE: DETERMINE THE MINIMUM SAMPLE SIZE

3. A doctor wants to estimate the HDL cholesterol of all 20- to 29- year-old females. How many subjects are needed to estimate the HDL cholesterol within 4 points with 99% confidence assuming standard deviation sigma = 19.4? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required?

(Round to the next whole number)

STUDY PLAN: 6.1.53, 6.1.56

OBJECTIVE: FIND A CRITICAL VALUE

4. Find the critical value tc for the confidence level c= 0.80 and sample size n= 17

(Round to the nearest thousandth as needed)

STUDY PLAN: 6.2.1, 6.2.3

OBJECTIVE: CONSTRUCT AND INTERPRET CONFIDENCE INTERVALS FOR THE POPULATION MEAN

5. The monthly incomes for 12 randomly selected people, each with a bachelor

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