A sample of 150 brand A lamps showed a mean lifetime of 1400 hours; a sample of 200 brand B lamps showed a mean lifetime of 1200 hours. For similar past studies, the population standard deviation for brand A lamps is assumed to be 120 hours; the population standard deviation for brand B lamps is 80 hours Find 99% confidence limits for the difference of the mean lifetimes of the populations of brands A and B Lower Limit of the CI = 167.4 Upper Limit of the C I = 232.6 Lower Limit of the CI = 67.78 Upper Limit of the CI = 32.69 Lower Limit of the CI = 107 Upper Limit of the CI= 139 None

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
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A sample of 150 brand A lamps showed a mean lifetime of 1400 hours;
a sample of 200 brand B lamps showed a mean lifetime of 1200 hours.
For similar past studies,
the population standard deviation for brand A lamps is assumed to
be 120 hours; the population standard deviation for brand B lamps
is 80 hours Find 99% confidence limits for the difference of the
mean lifetimes of the populations of brands A and B
Lower Limit of the CI = 167.4
Upper Limit of the C I = 232.6
Lower Limit of the CI = 67.78
Upper Limit of the CI = 32.69
Lower Limit of the CI = 107
Upper Limit of the CI = 139
None
Transcribed Image Text:A sample of 150 brand A lamps showed a mean lifetime of 1400 hours; a sample of 200 brand B lamps showed a mean lifetime of 1200 hours. For similar past studies, the population standard deviation for brand A lamps is assumed to be 120 hours; the population standard deviation for brand B lamps is 80 hours Find 99% confidence limits for the difference of the mean lifetimes of the populations of brands A and B Lower Limit of the CI = 167.4 Upper Limit of the C I = 232.6 Lower Limit of the CI = 67.78 Upper Limit of the CI = 32.69 Lower Limit of the CI = 107 Upper Limit of the CI = 139 None
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