# What are two things that can affect the range (i.e., width) of a confidence interval. Explain your answer.

Part A
Using an example (be creative) define and explain degrees of freedom.

The formula for calculating degrees of freedom for this assignment is N – 1.

If N = 10 and the mean of your sample = 77.1, solve for the score X below.
52, 5, 97, 175, 40, 104, 130, 39, 117, X

X = ? (Hint, the answer is not 9).

Part B
Compare and contrast directional and nondirectional hypotheses. Provide an example of a directional and of a nondirectional hypothesis.

Part C
What is the difference between probability and nonprobability sampling?

Provide an example of probability and an example of nonprobability sampling.

What is the best type of sampling procedure a researcher can use to generalize from a sample to a population? Why?

Part D
What are confidence intervals?

What are two things that can affect the range (i.e., width) of a confidence interval. Explain your answer.

A newspaper report is concerned with whether adults think children under 10 should drink caffeine. Of the 3,000 adults who participated in this study, 73% thought that children under 10 should not drink caffeine. The report claimed that the margin of error for this result is 5%.

What is the confidence interval for this report (i.e., report the actual range of scores)?

In order for this result to be generalizable from the sample of 3,000 to the population of interest, what type of sampling technique should be used? Why? 