99% Confidence Interval for HR

SEM for n=25

Z for 99% CI

Z * SEM

1.37

????????????

2.576

 

Lower Limit

µ - [Z*SEM]

Mean

Upper Limit

µ + [Z*SEM]

83.00

90.7

84.26

answer the question box

The breaking strengths of cables produced by a certain manufacturer have a standard deviation of 91 pounds. A random sample of 80 newly manufactured cables has a mean breaking strength of 1750 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.)

I need both the lower limit, and upper limit of the 90% confidence interval.

1. A sample of size n=49 is drawn from a population whose standard deviation is .

(a) Find the margin of error for a 95%confidence interval for .

b) If the sample size were n=60, would the margin of error be larger would be larger or smaller.

2.  Determine the point estimate of the population mean and margin of error for the confidence interval. The lower bound is 23; the upper bound is 27. The point estimate of the population mean is? The margin of error for the confidence interval is?

A simple random sample of size n is drawn from a population that is known to be normally distributed. The sample mean, x¯\bar{x}xˉ, is determined to be 104.3 and the sample standard deviation, s, is determined to be 15.9. (a) Construct the 90% confidence interval for the population mean if the sample size, n, is 15. (b) Construct the 90% confidence interval for the population mean if the sample size, n, is 25. How does increasing the sample size affect the width of the interval? (c) Construct the 95% confidence interval for the population mean if the sample size, n, is 15. Compare the results to those obtained in part (a). How does increasing the level of confidence affect the confidence interval? (d) Construct the 90% confidence interval for the population standard deviation if the sample size, n, is 15.�