Wednesday = Study!

Tomorrow we will start class with a (10 minute quiz)--there are three questions:

• Determine if a confidence interval is appropriate (know the name of this type of interval)
• Interpret the meaning of a given interval
• Identify the values of x, n, and p-hat for a given context

To study you can complete the practice quiz provided below! I added two extra questions (in red) to better reflect tomorrow's quiz.

Pop Practice Quiz! Context and Confidence Intervals!

A Rutgers University study released in 2002 found that many high-school students cheat on tests. The researchers surveyed a random sample of 4500 high school students nationwide; 74% of them said they had cheated at least once.

1.       Identify the sample size and describe the sample from which we obtained our data. (2 points)

2.       Define the population of interest. (2 points)

3.       What is the population parameter of interest? That is, what (type of) value are you trying estimate (about the population)? (2 points)

4.       Identify each of the following: (3 points)

   n = ___________                x = ___________          p-hat = ____________    

5.       Verify that the conditions for a one-proportion z-interval are satisfied. BE DETAILED in your explanations! (6 points)         

6.       Create a 98% confidence interval to estimate the proportion of high school students nationwide who have cheated at least once.

7.       A 98% confidence interval was created to estimate the proportion of high school students nationwide who have cheated at least once. Interpret the meaning of this interval: (0.72479, 0.75521)

And here are the answers to the practice quiz!

1. Sample: 4500 high school students selected from across the nation
2. Population of Interest: all high school students nationwide
3. Parameter of Interest: % of all high school students nationwide who have cheated (on tests) at least once
4. n = 4500, p-hat = 0.74 or 74%, x = (0.74)(4500) = 3330
5. Researchers surveyed a random sample of 4500 high school students, 4500 is < 10% of all high school students nationwide, and (4500)(0.74)>10 and (4500)(1-0.74)>10; therefore, a one proportion z interval IS appopriate.
6. Interval = (0.72479, 0.75521) (Use OnePropZInt on your calculator to get this)
7. We are 98% confident that the true proportion of high school students nationwide who have cheated (on tests) at least once falls between 72.479% and 75.521% based on this sample of 4500 high school students.

Tomorrow in class (after our 10 min quiz) it's all about the formula! I can't wait--see you there!