Answer Key on Probability Sampling

Instructions: Answer the following questions using the information provided.

You have just taken a random sample of a two hundred DePaul students and asked them three questions. You obtained the following responses with the corresponding sampling errors.

a. 60% of your sample supports pro-choice group on campus (sampling error = 10).

b. 90% of your sample would like to switch to a semester system (sampling error = 1).

c. 15% of your sample favors raising tuition (sampling error = 2).

1. For each response you obtained from the voters, provide the appropriate confidence intervals.

a. What percentage of students support a pro-choice group on campus given a 95% confidence level?

_40_ to _80__

b. What percentage of students would like to switch to semester system given a 68% confidence level?

_89__ to _91__

c. What percentage of students favor raising tuition given a 99% confidence level?

_9___ to __21_

2. Now provide the appropriate confidence level associated with following the following confidence intervals for each question.

a. How confident are you that 50 to 70% of the students support a pro-choice group on campus? _68___

b. How confident are you that 87 to 93% of the students want to switch to a semester system? __99__

c. How confident are you that 11 to 19% of the students want tuition to increase? __95_

3. Assume that you ask four of your friends how much money they won in Las Vegas over the weekend. You received the following answers. $20, 0, -20, -10.

What is the probability (chance) that if you selected a sample of two of your friends, that their average response would be that they won $10? 1 out of 6

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