標題:

Statistics

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FURTHER POST A STATISTICS QUESTION (unable to understand from the previous reply & thus pls kindly explain with detailed steps, PLUS wordings ). TKS! ==> Mean life of a shipment of lamps: 375 hr==> The process standard deviation: 100 hr==> A random sample of 64 lamps has a sample mean life of 350... 顯示更多 FURTHER POST A STATISTICS QUESTION (unable to understand from the previous reply & thus pls kindly explain with detailed steps, PLUS wordings ). TKS! ==> Mean life of a shipment of lamps: 375 hr ==> The process standard deviation: 100 hr ==> A random sample of 64 lamps has a sample mean life of 350 hr. (i) What are the null & alternative hypotheses? <== pls kindly explain the terms with wordings as well. (ii) at 0.05 level of significance, is there evidence with the mean life to be different from 375 hr? (iii) set up a 95% confidence interval so as to estimate the population mean life of the lamps. (iv) by comparing the outcomes of (ii) & (iii), pls draw the conclusions.

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最佳解答:

i) Null hypothesis H0: Mean life μ = 375 hrs (which is the same as the given statement) Alt. hypothesis H1: Mean life μ =/= 375 hrs (which is in opposition to H0). ii) standard devistion of the mean life of the sample of 64 lamps = 100/√64 = 12.5 hours Since we are testing for if μ = 375 or not, 2-tail test will be applied, i.e. Sampled standard score z = (350 - 375)/12.5 = -2 <= -1.96 (5% sig. level for 2-tail test) Hence there is evidence that the mean life is different from 375 hours. iii) 95% confidence interval = 350 +/- 1.96 x 12.5 i.e. 325.5 <= μ <= 374.5 iv) H1 is accepted at 5% level of significance.

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