1 / 14

What Are We Summarizing?

What Are We Summarizing?. Lecture 13 Sections 4.1 – 4.2 Wed, Sep 12, 2007. What Are We Summarizing?. How can we summarize data taken from a sample? We want to reduce the data down to a single number (a statistic). What Are We Summarizing?. How best to summarize… Political affiliation?

duscha
Download Presentation

What Are We Summarizing?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. What Are We Summarizing? Lecture 13 Sections 4.1 – 4.2 Wed, Sep 12, 2007

  2. What Are We Summarizing? • How can we summarize data taken from a sample? • We want to reduce the data down to a single number (a statistic).

  3. What Are We Summarizing? • How best to summarize… • Political affiliation? • Body weight? • Steak preference (rare, medium, etc.)? • Number of children? • Temperature throughout the day? • What is the difference?

  4. Qualitative Variables • Qualitative variable. • The values of a qualitative variable may or may not have a natural order. • Examples: • Political affiliation. • Steak preference.

  5. Summarizing Qualitative Variables • Typically, we use percentages or proportions to summarize qualitative variables. • 40% of the subjects are Democrats. • 50% of the people prefer their steak medium.

  6. Quantitative Variables • Quantitative variable. • The values of a quantitative variable always have a natural order. • Examples: • A person’s weight. • Number of children. • Temperature.

  7. Summarizing Quantitative Variables • Typically, we use averages to summarize quantitative variables. • The people in the sample weigh an average of 156.2 lbs. • The people in the sample have an average of 2.3 children. • The average temperature for the day was 82.7 degrees F.

  8. Caution • Some qualitative variables may appear to be quantitative. • Rate your own sexual desire: • (1) Way below average • (2) Below average • (3) Average • (4) Above average • (5) Way above average

  9. Caution • If one person selects (2) and another person selects (4), does that mean that the second person has twice the sexual desire as the first person?

  10. Quantitative Variables • A quantitative variable may be continuous or discrete.

  11. Continuous Variables • Continuous variable. • Typically these are measured quantities: length, time, area, weight, etc.

  12. Discrete Variables • Discrete variable. • Typically these are count data • A verbal description usually contains the phrase “the number of.”

  13. Discrete vs. Continuous • Some data may mistakenly be thought to be discrete. • Time • Weight • Clearly, all measurements must be rounded off. But that does not make the quantity itself discrete.

  14. Discrete vs. Continuous • What about heart rate, measured in beats per minute? • It is the basic nature of the quantity that matters, not how we choose to record our observations.

More Related