While measuring specimens of nylon yarn taken from two spinning machines, it was found that 9 specimens from the first machine h
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Answer:
A sample size of 128 is needed.
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(square root of the variance) and n is the size of the sample.
How large should a sample be if the margin of error is 1 minute for a 93% confidence interval
We need a sample size of n, which is found when . We have that
. So
Rounding up
A sample size of 128 is needed.