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Unformatted text preview: 1. 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) a. 90% 1 sided confidence interval: z = 1.282 b. 80% 1 sided confidence interval: z = 0.842 2. 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 er or E for a 90% confidence interval. (5 points) Round your answer to the nearest hundredths. . (References: definition of margin of er or on page 312 and example 2 on page 312). The standard deviation is not given, but necessary to answer this question. Some people use the zdistribution here instead of the more appropriate tdistribution, in which case you should replace 1.677 with 1.645. b. Construct a 90% confidence interval for the mean life, ? of al Twinkle bulbs. (5 points) (References: example 5 page 315, end of section exercises 51  56 pages 319  320) b....
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This note was uploaded on 11/07/2011 for the course ACC 220 taught by Professor  during the Spring '10 term at University of Phoenix.
 Spring '10
 

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