1. Definition of Statistics
Statistics is the science of:
- collecting
- organizing
- analyzing
- interpreting
data in order to make decisions.

2. Definition of Data
Data consist of information coming from observations, counts, measurements, or responses.

3. Data Sets Population: all outcomes, responses, measurements, or counts
Sample:
a subset, or part, of a population

4. Example What is the population? What is the sample?
A survey of 1000 adults found that 59% think buying a home is the best investment a family can make.
What is the population?
What is the sample?

5. Example What is the population? What is the sample?
A survey of 1000 adults found that 59% think buying a home is the best investment a family can make.
What is the population?
The set of responses of all adults in U.S.
What is the sample?

6. Example What is the sample?
A survey of 1000 adults found that 59% think buying a home is the best investment a family can make.
What is the sample?
The set of the responses of the 1000 adult surveyed.

7. Parameter versus Statistic
Parameter: a numerical description of a population characteristic
Statistic: a numerical description of a sample characteristic

8. Parameter versus Statistic (examples)
The 2009 payroll of the Philadelphia Phillies was $113,004,046.
Fifty percent of a sample of 1508 US adults say they oppose drilling for oil in the Arctic Wildlife Refuge.
In a recent study of math majors at a university, 10 students were minoring in physics.
In a survey of 752 adults 42% think there should be a law that prohibits people from talking on cell phones in public places.

9. Descriptive versus Inferential Statistics
Descriptive: branch of statistics that organizes and displays the data (describe)
Inferential: branch of statistics that involves using a sample to draw a conclusion about a population (infer)

10. Example
A tire manufacturer wants to estimate the average life of a new type of steel belted radial tire.
descriptive study? inferential study?

11. Will the manufacturer look at all tires?
A tire manufacturer wants to estimate the average life of a new type of steel belted radial tire.
Will the manufacturer look at all tires?
Will the manufacturer take a sample of tires, examine the sample, and then conclude something about all tires?
It is impractical to look at all/every tire. So one will take a reasonable and unbiased sample of the tires and examine the average age. From this sample average one can infer something about the age of all tires (the population).
Thus  an inferential study

12. Example
A sports writer plans to list the winning times for all the swimming events in the 2012 Olympics.
descriptive study? Inferential study?

13. A sports writer plans to list the winning times for all the swimming events in the 2012 Olympics.
The writer wants to simply organize the data and compile a list (describe!) of the medal winners of the Olympics
descriptive study

14. Descriptive versus Inferential
A survey conducted among 1017 men and women found that 76% of women and 60% of men had a physical examination with the previous year.
Inferential? Descriptive?

15. A survey conducted among 1017 men and women found that 76% of women and 60% of men had a physical examination with the previous year.
Inferential? Descriptive? Both!
76% women, 60% men  Descriptive (simply describes the data sample which was collected)
More women than men will have physical exams during the year  Inferential (use the data sample to say something about the population)