Testing the Manufacturing Quality Process
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A manufacturer receives an order for light bulbs. The order requires the bulbs have a mean life span of 750 hours. The manufacturer selects a random sample of 25 light bulbs and find they have a mean life of 745 hours with a standard deviation of 15 hours. Test to see if the manufacturer is making acceptable light bulbs. Assume the data are normally distributed. Show your curve. a=0.05
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Denote by mu the mean life span. Then we would like to test
H0: mu=750
Ha: mu is NOT equal to 750.
Now we use z-test. As the sample mean ...
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- BSc , Wuhan Univ. China
- MA, Shandong Univ.
Recent Feedback
- "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
- "excellent work"
- "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
- "Thank you"
- "Thank you very much for your valuable time and assistance!"
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