1. Math CC7/8 – Be Prepared
On Desk:
Pencil
Calculator
Math Journal
SP Learning Log
2.4 WS on counter
Learning Log:
HW: Page 47 #15-17, #34-37
Turn in Partner Quiz!! Due today. (1pt off per day late)

2. Tasks for Today
Lesson 2.4 – What Sample Size to Use?

3. Summary of lesson 2.3 – Choosing Random Samples
We had many different random samples of 30 from the population of 100. (movies & sleep)
Were our samples the same, or was there variance amongst our samples?
Do you think some samples were a better representation of the population than others?
Conclusion:
Sampling is a good technique in general, but it can occasionally lead to drawing poor conclusions.

4. Materials needed: 10-section spinner (0-9)
Labsheet 2.3 A (movie & sleep data – 100 students)

5. Adapted: Movie data only, same partners!
Spin to find student numbers for sample of 5 students
Record their movie data
Spin to find student numbers
for sample of 10 students
Record their movie data
Record this data
in your journal.
Student #
# of Movies 1. 2. 3. 4. 5. 6. 7. 8. 9.
10.
Student #
# of Movies 1. 2. 3. 4. 5.

6. B.
Find the mean of each sample (5 and 10 and 30).
Record your groups statistics on the class chart. (Labsheet 2.4F)

7. The means for samples of 5 should show considerable variation.
Labsheet 2.4A for line plots of means of 5, 10, and 30
The means for samples of 5 should show considerable variation.
The means for samples of 10 should show less variation than 5, but more than the means for samples of 30.
The means for samples of 30 should cluster near the population mean of about 4.

8. The larger the sample size from which the means are drawn, the better the estimate of the mean for the entire population.

10. With a sample size of 50, the mean number of movies watched would show less variation than the line plots of a size of 30. There would probably be a more pronounced clustering around 4.

11. The variability drops as the sample size increases.
The characteristics of the sample become closer to those of the population as a whole.