Carry your intermediate computations to at least three decimal places. Round you

Question

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

(If necessary, consult a list of formulas.)

What is the upper limit of the 95 % confidence interval?

The breaking strengths of cables produced by a certain manufacturer have a standard deviation of 81pounds. A random sample of50 newly manufactured cables has a mean breaking strength of 1850
pounds. Based on this sample, find a 95% confidence interval for the true mean breaking strength of all cables produced by this manufacturer. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

(If necessary, consult a list of formulas.)

Explanation / Answer

Mean is 1850 and s is 81

for sample size of 50, the standard error SE=s/sqrt(N)=81/sqrt(50)=11.455

z for 95% confidence is 1.96

thus the lower limit is mean-SE*Z =1850-11.455*1.96=1827.5482

the upper limit is mean+SE*Z =1850+11.455*1.96=1872.4518

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