The critical value tt for a 90% confidence interval and a sample size of 20 estimate is 1.725 1.645 1.729 2.086 2.093

In a sample of 10 randomly selected black bears from northeast Pennsylvania, the sample mean was 214.1 pounds and the sample standard deviation was 51.1 pounds. Construct a 99% confidence interval estimate for the population standard deviation of all black bears in this region.

Estimate the minimum sample size needed to achieve the margin of error E=0.013 for a​ 95% confidence interval.

A sample of   children aged 8 - 10 living in New York is needed to obtain a 99% confidence interval with a margin of error of 0.02 when no estimate of p is available.

Estimate the minimum sample size needed to achieve the margin of error E = 0.026 for a 95% confidence interval. The minimum sample size is (Round up to the nearest integer.)

Total plasma volume is important in determining the required plasma component in blood replacement therapy for a person undergoing surgery.  Plasma volume is influenced by the overall health and physical activity of the individual.  Suppose that a random sample of 45 male firefighters was tested and the sample mean was 37.5 ml/kg.  Assuming that the population standard deviation for the distribution of blood plasma is 7.5 ml/mg.  Find a 99% confidence interval for the mean blood plasma volume in male firefighters.

Find the critical value for a 98% confidence interval. Then calculate the interval.

A 90% confidence interval for p=0.37 and n=475

Unoccupied seats on flights cause airlines to lose revenue. Suppose a large airline wants to estimate its mean number of unoccupied seats per flight over the past year. To accomplish this, the records of 225 flights are randomly selected and the number of unoccupied seats is noted for each of the sampled flights. The sample mean is 11.6 seats and the sample standard deviation is 4.1 seats. Construct a 92% confidence interval for the population mean number of unoccupied seats per flight. (Round your answers to one decimal place.) margin of error E = Lower limit = Upper limit =

In a random sample of 19 people, the mean commute time to work was 32.5 minutes and the standard deviation was 7.1 minutes. Assume the population is normally distributed and use a​ t-distribution to construct a 95​% confidence interval for the population mean μ. What is the margin of error of μ​? Interpret the results.