Mrs. Trout estimated her math class next year would include 28 students. The actual size of the class turned out to be 32 studen
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Answer:
The 95% confidence interval estimate of the population mean life of the new light-bulb is (469.21 hours, 510.79 hours).
This confidence level means that we are 95% sure that the true population mean life of the new light bulb is in this interval.
Step-by-step explanation:
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of .
So it is z with a pvalue of , so
Now we find M as such:
In which is the standard deviation of the population and n is the length of the sample. So:
The lower end of the interval is the mean subtracted by M. So it is 490 - 20.79 = 469.21 hours.
The upper end of the interval is the mean added to M. So it is 490 + 20.79 = 510.79 hours.
The 95% confidence interval estimate of the population mean life of the new light-bulb is (469.21 hours, 510.79 hours).
This confidence level means that we are 95% sure that the true population mean life of the new light bulb is in this interval.