Which is the better buy? 12 bars of soap for $10.00 or 5 bars of soap for $4.00
2 answers:
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Answer:
The 95% confidence interval for the population mean is between 25.86 and 28.14.
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, find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 27 - 1.14 = 25.86
The upper end of the interval is the sample mean added to M. So it is 27 + 1.14 = 28.14
The 95% confidence interval for the population mean is between 25.86 and 28.14.