Total points are 40. Points are included with each problem.
Included with each section or problem are reference examples and end of section exercises that can be used as a guide. Be sure to show your work in case partial credit is awarded. To receive full credit, work must be shown if applicable.
Section 6.1: Confidence Intervals for the Mean (Large Samples)
Find the critical value zc necessary to form a confidence interval at the given level of confidence. (References: definition for level of confidence page 311, end of section exercises 5 – 8 page 317) (2.5 points each)
½ (1-.90) = 0.05 = 1.645
½ (1-.80) = 0.10 = 1.28
The new Twinkle bulb has a standard deviation hours. A random sample of 50 light bulbs is selected from inventory. The sample mean was found to be 550 hours.
a. Find the margin of error E for a 90% confidence interval. (5 points)
Round your answer to the nearest hundredths. . (References:
definition of margin of error on page 312 and example 2 on