1. Data Collection Statistics
11/28
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
LESSON
Data Collection
In research, statisticians use data in many different ways.
Data can be used to describe situations.
Data can be collected in a variety of ways, BUT if the sample data is not collected in an appropriate way, the data may be so completely useless that no amount of statistical torturing can salvage them.

2. Random Sampling Selected by using chance or random numbers
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Random Sampling
Selected by using chance or random numbers
Each individual subject (human or otherwise) has an equal chance of being selected
Examples:
Drawing names from a hat
Random Numbers

3. Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Systematic Sampling
Select a random starting point and then select every kth subject in the population
Simple to use so it is used often

4. Convenience Sampling Use subjects that are easily accessible Examples:
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Convenience Sampling
Use subjects that are easily accessible
Examples:
Using family members or students in a classroom
Mall shoppers

5. Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Stratified Sampling
Divide the population into at least two different groups with common characteristic(s), then draw SOME subjects from each group (group is called strata or stratum)
Basically, randomly sample each subgroup or strata
Results in a more representative sample

6. Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Cluster Sampling
Divide the population into groups (called clusters), randomly select some of the groups, and then collect data from ALL members of the selected groups
Used extensively by government and private research organizations
Examples:
Exit Polls

7. Types of Experiments Observational Studies
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Types of Experiments
Observational Studies
The researcher merely observes what is happening or what has happened in the past and tries to draw conclusions based on these observations
No interaction with subjects, usually
No modifications on subjects
Occur in natural settings, usually
Can be expensive and time consuming
Example:
Surveys---telephone, mailed questionnaire, personal interview

8. More on Surveys Telephone Mailed Questionnaire Personal Interviews
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
More on Surveys
Telephone
Mailed Questionnaire
Personal Interviews
Less costly than personal interviews
Cover a wider geographic area than telephone or pi
Provides in-depth responses
Subjects are more candid than if face to face
Less expensive than telephone or pi
Interviewers must be trained
Challenge---some subjects do not have phone, will not answer when called, or hang up (refusal to participate)
Subjects remain anonymous
Most costly of three
Tone of voice of interviewer may influence subjects’ responses
Challenge –low number of subjects’ respond, inappropriate answers to questions, subjects have difficulty reading/understanding the questions
Interviewer may be biased in his/her selection of subjects

9. Interaction with subject occurs, usually
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Experimental Studies
The researcher manipulates one of the variables and tries to determine how the manipulation influences other variables
Interaction with subject occurs, usually
Modifications on subject occurs
May occur in unnatural settings (labs or classrooms)
Example:
Clinical trials of new medications ,treatments, etc.

10. So once we’ve collected the data, what does it look like?
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
So once we’ve collected the data, what does it look like?
A frequency distribution is symmetric when a vertical line can be drawn through the middle of a graph of the distribution and the resulting halves are approximately the mirror images.
A frequency distribution is uniform (or rectangular) when all entries, or classes, in the distribution have equal frequencies. A uniform distribution is also symmetric.
A frequency distribution is skewed if the “tail” of the graph elongates more to one side than to the other. A distribution is skewed left (negatively skewed) if its tail extends to the left. A distribution is skewed right (positively skewed) if its tail extends to the right.

11. Symmetric Distribution
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Symmetric Distribution
10 Annual Incomes
15,000
20,000
22,000
24,000
25,000
26,000
28,000
30,000
35,000
Income 5 4 3 2 1 f
$25000
mean = median = mode
= $
25,000

12. Skewed Left Distribution
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Skewed Left Distribution
10 Annual Incomes
20,000
22,000
24,000
25,000
26,000
28,000
30,000
35,000
Outlier
Income 5 4 3 2 1 f
$25000
mean = $_______
median = $_______
mode = $________
23,500
25,000
Mean ___ Median
<
25,000

13. Skewed Right Distribution
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Skewed Right Distribution
10 Annual Incomes
15,000
20,000
22,000
24,000
25,000
26,000
28,000
30,000
1,000,000
Income 5 4 3 2 1 f
$25000
121,500
mean = $_______
median = $_______
mode = $______
Mean ____ Median
>
25,000
25,000

14. Summary of Shapes of Distributions
Objective: Students will be able to identify 5 basic sample techniques, observational and an experimental study. Students will also explore mean, median, and mode.
Standards: 1.02 Summarize and analyze univariate data to solve problems
Essential Question: How do you determine which sample to use?
Summary of Shapes of Distributions
Symmetric
Uniform
Mean = Median
Skewed right
Skewed left
VERY IMPORTANT!!!
Mean > Median
Mean < Median

15. Homework:
Poll 50 people (keep their ages) on whether they voted Republican (Donald Trump), Democratic (Hillary Clinton) or Libertarian (Gary Johnson) for the presidential election.
Make a Google Sheet that includes:
ID Number
Age
City of Residence
Voter choice
Answer the following questions in complete sentences:
Explain how you completed your data collection.
What data collection method did you use? Explain why you used that method.