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7th Grade Math / Lesson 7: Sampling and Predicting

SAMPLING & PREDICTING
What will we be learning in this lesson?


  • In this lesson you will learn how to find a sample population to make a prediction on a larger group.
Vocabulary words are found in this purple color throughout the lesson. Remember to put these in your notebook.


SAMPLING & PREDICTING


  • If you want to make a prediction about a large group of people, you may wish to use a smaller group, or sample, from the larger group. The large group from which you gathered your sample is known as the population. To make sure your information represents the population, the sample must be drawn at random. A random sample gives everyone the same chance of being selected.


SAMPLING & PREDICTING


  • Suggestions for drawing a random sample.

    Suppose you need to find out what is the most popular meal in your school's cafeteria. To get a random sample, you could

    1. Survey every fifteenth student named on the school roster.
    2. Survey every tenth student in the lunch line at the cafeteria.
    3. Survey two students from each homeroom class

    Each of these methods ensures that everyone has an equal chance of being selected for the survey.


SAMPLING & PREDICTING


  • Practice
    Mathville Middle School's newspaper surveyed the school's students by asking them what their favorite type of music is. The school has 1,020 students.



    a. What was the sample size?
    b. To the nearest percent, what percent of students preferred pop?
    c. How many students in the school would you expect to say that pop is their favorite?


SAMPLING & PREDICTING


  • Practice
    Mathville Middle School's newspaper surveyed the school's students by asking them what their favorite type of music is. The school has 1,020 students.



    a. What was the sample size?
    151 students (add the numbers)
    b. To the nearest percent, what percent of students preferred pop?
    59/151 = .39 39%
    c. How many students in the school would you expect to say that pop is their favorite?
    39% of 1,020 = 398


SAMPLING & PREDICTING


d. If the school newspaper had only surveyed students from some boys' health education classes, would that be a random sample? Explain.

Not random. Not all students have an equal opportunity to be chosen.

e. About how many students in the school would you expect to say that country is their favorite?

32/ 151 = .21 which is 21%

21% of 1,020 is 214

214 students would say country


  • Can you find a sample of a certain population?
  • Can you determine if a sample is random?
  • Go back to the classroom to get to your homework and any other items you need to attend to.