A technician in a light bulb manufacturing plant desires to determine the mean lifetime of the light bulbs in the most recent production run. The technician takes an SRS of 20 light bulbs. The mean and standard deviation of this sample is 72 hours and 15 hours respectively.
What is the 99% confidence interval for the mean lifetime ( µ ) for all light bulbs in this production run?
The critical value is obtained from students t table for alpha=0.005 and 19 degrees of freedom.
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