3. Homework 5/24/17
Worksheet: Independent and Dependent Events Worksheet #4
YOU HAVE A QUIZ TOMORROW! Independent and Dependent Event.

4. Biased or Unbiased?
The mayor surveys 100 supporters at a rally about the most important issues to be addressed by the city council.
The principal sends out questionnaires to all of the students to find out what kind of music students prefer at dances.
The owner of a record shop surveys only customers over the age of 18 who shop at his store.
The teacher writes the name of each student on a piece of paper and questions the students whose names are drawn.
A convenience store surveys customers one morning to determine what products they may like the store to stock.
Each student’s name is written on a slip of paper and placed in a box. One slip of paper is selected to determine the student to be the homeroom representative.

5. Biased or Unbiased?
A company randomly selects 500 customers from its database and then surveys these customers to find out how they like their service. Unbiased
A city-hall employ surveys 100 customers at a restaurant to learn about the jobs and salaries of city residents Biased
A newspaper randomly chooses 100 names from a subscriber database and then surveys those subscribers to see if they read the restaurant reviews. Unbiased

6. Predicting Proportion:
x (prediction)
sample piece
sample size
entire population

7. Example: A university has 30,600 students
Example: A university has 30,600 students. In a random sample of 240 students, 20 speak 3 or more languages. Predict the number of students at the university that speak 3 or more languages.
x = 2550 students

8. There are 4500 elk located on a preserve in Colorado
There are 4500 elk located on a preserve in Colorado. A biologist thinks that the herd may be infected with parasite. She does a random sample of 50 elk. If she discovers that 8 of the sample is infected. Predict how many elk the biologist can expect to be infected.
720 elk are infected

9. A factory produces 150,000 light bulbs per day
A factory produces 150,000 light bulbs per day. The manager estimates that less than 1,000 defective bulbs are produced each day. In a random sample of 250 light bulbs, there are 2 defective bulbs. Determine if the manager's estimate is likely to be accurate. Explain.
His estimate is incorrect. There are at least 1200 defective bulbs each day.

10. A middle school has 2,500 students
A middle school has 2,500 students. Morgan interviewed 75 students about their library habits. She found that 45 of the students checked out a book weekly. Predict the number of students likely to check out books weekly.
1500 students

11. Zack chooses a random sample of 50 out of 400
students. He finds that 7 of them have traveled to a foreign country. Zack claims that more than 50 of the 400 students have traveled to a foreign country. Do you agree with his answer? Explain.
Yes. 56 students have traveled.

12. What color is your hair? Brown ______ Blond ______ Red ______ Black _______
Do you carry a cell phone? Yes______ No _________
About how many text messages do you send in a day? 0-20 _____ ______ >40 ______
About how much time do you spend on homework? 0-15 min _____ min _____ min ______ min _______ > 60 min ______
What month were you born? Jan – March _____ April – June _____ July-Sept. _____Oct-Dec ______

13. Using the survey results discuss the following vocabulary.
What is the population of your survey?
The population is the entire class. Population is the entire set of
items for which data can be collected.
Did your class perform a census or a survey? A census means you ask everyone in the population. Survey means you ask a representative sample of the population.
This is a census.
How would you describe your results from question 2 as a parameter
for the population? A parameter means you describe a characteristic about the population based on your data.
Most seventh grade students carry a cell phone.

14. The manager of the Millcreek Mall wants to know the mean age of the people
who shop at the mall and the stores in which they typically shop. He hires
Barker Market Research Company to collect the data. Dennis works for the
Barker Market Research Company and has been put in charge of collecting data
for the Millcreek Mall. Dennis decides to interview 100 people one Saturday
because it is the mall’s busiest shopping day.
Is the survey a sample or a census?
It is a sample.
What is the population for this survey?
The population is everyone who comes to the mall.
Is the sample size for the survey appropriate?
The sample size is too small for the population. The 100 people are not a representative sample of the entire population.