1. 5.1 – Designing Samples

2. Observe individuals and measure variables of interest, but do not attempt to influence the responses
____________
___________
Deliberately impose some treatment in order to observe their responses

3. Entire group of individuals that we want information about
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Part of the population that represents the population of interest
___________
Studying a part in order to gain info about the whole
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Attempts to contact every individual in the entire population

4. ___________________
Process used to choose the sample from the population
___________________
Systematically favors certain outcomes

5. ____________________________
People who choose themselves by responding to a general appeal.
Biased because people with strong opinions, especially negative ones, are more likely to respond.

6. ________________________
Choosing individuals who are easiest to reach

7. ______________________________
Consists of n individuals from the population chosen in such a way that every set of n individuals has an equal chance to be in the sample selected
Each group AND each person in each group has an equal chance!

8. _________________________
A table with a long string of digits 0-9 where:
Each entry in the table is equally likely to be chosen
The entries are independent of each other

9. Choosing an SRS
1. Label. Assign a number to each individual
2. Table. Use Table B to select labels at random
3. Stopping Rule. Know when to stop sampling
4. Identify Sample. Use the labels to identify the subjects

10. Calculator Tip: Random Integers
Math – Prob – RandInt (smallest #, largest #, n)

11. Example #1
Suppose I wish to choose ten people from three Statistics classes to receive a bonus of 20 extra credit points. Picking the first 10 students that come to mind would be biased and unfair. How do I get a SRS where everyone would have an equal chance to receive the extra credit?

12. We must use the Random Number Table
STEPS:
Suppose there are a total of 90 students in Statistics. We must assign each student name a number:
01, 02, 03, 04, 05, …… 55, 56, 57 ……… 88, 89, 90
Randomly choose a row and column to start on in the random number table: Row109, Column 1.

14. ______ _______ ______ _______ _______
Enter the numbers you read (in pairs) horizontally:
______ _______ ______ _______ _______
If you complete a whole row and need to keep going, drop down to the beginning of the next row.
If the number is not in your range, ignore it and move to the next two digits.
If the number is a repeat of one you already selected, skip it and move to the next two digits.

16. ______ _______ ______ _______ _______ 36 00 91 93 65
Enter the numbers you read (in pairs) horizontally:
______ _______ ______ _______ _______ 36 00 91 93 65 15 41 23 96 38 85 45 34 68 16
If you complete a whole row and need to keep going, drop down to the beginning of the next row.
If the number is not in your range, ignore it and move to the next two digits.
If the number is a repeat of one you already selected, skip it and move to the next two digits.

17. _______________________
The population is first separated into groups with similar characteristics, called STRATA and then a SRS is done within each stratum. The samples are combined to make the full sample. There is little variability inside the strata, but is variability between the strata.
Men
Choose 50
Women
Choose 50

18. ______________________
Divides the population into groups or clusters. There is variability in the cluster, little difference between clusters. All the individuals in the randomly chosen clusters are selected.
AP Stats - SRHS
AP Stats - WRHS
AP Stats - NRHS
AP Stats - ERHS

19. ___________________________
Choose an n to start with and then survey every nth person after that.

20. _____________
When some groups in the population are left out of the process of choosing the sample
____________
When an individual chosen for the sample can’t be contacted or does not cooperate.

21. ___________________
When the interviewer influences the response. (i.e. Female surveying male)
____________________
Leading questions or the wording of the question that elicit a specific answer