1. A local college is conducting a study of several characteristics of its student body. A sample of 100 students is taken. The study finds that 14 of these students smoke.
a. Find the point estimate of the proportion of college students who smoke.
b. In constructing 95% confidence interval for the proportion of college students who smoke, what is the critical value?
c. In constructing 95% confidence interval for the proportion of college students who smoke, find the margin of error.
d. Construct a 95% confidence interval estimate for the proportion of college students who smoke.
e. Interpret the confidence interval. (Read interpreting a confidence interval on p.318 textbook.)
f. Would it be correct to state in the college newspaper that less than half the students smoke? Explain your answer.
2. How large a sample should be taken in order to be 90% confident that a proportion interval has a margin of error of three percentage points? Assume that a previous study suggested that the proportion is 60%.
3. How large a sample should be taken in order to be 95% confident that the sample proportion has a margin of error of three percentage points? Assume that there is no available information that can be used to estimate the proportion.
4. Find the critical value ta/2 for the confidence interval for the mean. Use t-table.
a. 99% confidence n=22
b. 95% confidence n=30
c. 98% confidence n=9
5. A study was conducted to determine the mean height of males suffering from Achondroplasia. The heights are normally distributed. A sample of 51 males was randomly selected from all the recorded cases at a large medical facility. The height of each man was recorded. The sample mean was 130 centimeters, and the sample standard deviation was 2.4 cm.
a. What is the point estimate of mean height?
b. In constructing a 95% confidence interval for population mean, find the degree of freedom.
c. In constructing a 95% confidence interval for population mean, find the critical value.
d. In constructing a 95% confidence interval for population mean, calculate the margin of error.
e. Construct 95% confidence interval for population mean.
f. Interpret the confidence interval in part e.