A sample of 8 adult elephants had an average weight of x = 12300 pounds. The sample standard deviation was s = 22 pounds. Construct a 99% confidence interval for the true population mean of the weights of adult elephants.

Suppose that you randomly survey death records for people born in 1900 in Louisiana and compared the life span of two different ethnicities. Of the 109 individuals sampled from ethnicity 1, the mean life span was 45.5 years with a standard deviation of 18.2 years. Of the 105 individuals sampled from ethnicity 2, the mean life span was 44.9 years with a standard deviation of 11.4 years. Conduct a hypothesis test with a 10% level of significance to see if the mean life spans in Louisiana were the same for the two ethnicities. Step 1: State the null and alternative hypotheses. Ho: µ1 – µ2 =v Ha:H1 – µ2 # v (So we will be performing a two-tailed ♥ test.)

A large number of bags of cement have been manufactured. You sample 10 of the bags and find that they have a mean weight of 91.5 pounds with a standard deviation of 8.8 pounds. Find the 90 % confidence limit for the mean of the weight of all of the cement bags.

Assume that adults have IQ scores that are normally distributed with a mean of 104.8 and a standard deviation 21.9. Find the first quartile Q1​, which is the IQ score separating the bottom​ 25% from the top​75%

The shelf life of a battery produced by one major company is known to be Normally distributed, with a mean life of 3.5 years and a standard deviation of 0.75 years. What is the upper quartile of battery shelf life? Use the fact that the middle 50% of the data falls within 0.67 standard deviations from the mean.

How can we also find normality?

A forestry researcher is conducting a study of trees in the upper midwest. He selects a random sample of 125 red maple trees and measures the trunk diameter of each. The mean of the sample is 25 inches with a standard deviation of 5.2 inches, use this to find a 95% confidence interval for the mean trunk diameter of all red maple trees.

The average height of students at a university from an SRS of 14 students gave a standard deviation of 2.5 feet. Construct a 95% confidence interval for the standard deviation of the height of students at the university. Assume normality for the data.

The heights of 9 men were taken with sample mean of 165 cm and standard deviation 5 cm. The heights of 7 Japanese women were taken with sample mean of 150 cm and standard deviation 3 cm. Assuming that the population standard deviations for heights of men and women are both the same, construct the 95% confidence interval for the difference in mean heights between men and women.

The average hemoglobin reading for a sample of 20 LHS teachers was 16 g/100 ml, with a sample standard deviation of 2 grams. Find the 95% confidence interval of the true mean.