Stats HW!

Good work today! Tomorrow we'll continue to explore confidence intervals for proportions!

Tonight, please complete the worksheet provided in class; if you lost it (or were absent), you can find the questions below. Use the hints below for d,e,f--no effort, no credit! I know I haven't taught these (specifically), but I want you to figure them out!

**We did not cover d,e or f today in class. I want you to try to figure these out! Here are some hints**

• For d, you need to calculate margin of error; this is just a matter of using the part of the confidence interval formula that represents "margin of error," and then substituting in the correct values. For more info, look at page 436.
• Use the same confidence level (90%) as for a,b, and c.
• For e and f, you need to find the sample size, given a margin of error. You are not given "p" or "p-hat." In any situation like this, we'll use 0.5 for p and q (hat). This will give us a "conservative estimate of margin of error.
• You can see an example of this type of problem (done out) on page 442. Once you set up the equation, this becomes a margin of error question. 

Homework Questions:

AP Statistics Exam: Estimating Population Proportions

Complete each of the questions in the space provided. Remember to complete each problem thoroughly, checking all conditions and showing your work. Write neatly in the space provided. All conclusions should be written in complete sentences.

1.) 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.

a.) Create a 90% confidence interval for the level of cheating among high-school students. Assume the conditions for inference have been satisfied. You may use your graphing calculator to create your confidence interval, but still must show the formula with the appropriate values substituted)

b.) In a complete sentence, interpret your confidence interval from part a.

c.) A teacher surveys his students and finds that 68% of students have cheated on a test. Does this value seem reasonable? Surprising? Explain your reasoning.

d.) Suppose we sample 2,000 students and find that 67% have cheated. Calculate the margin of error.

e.) If we want to have a margin of error of only 3% and want 98% confidence, how large of a sample must be used?

f.) If we want to have a margin of error of 5% to create a 95% confidence interval, what is the appropriate sample size?