1 / 19

Frequency Distributions

Frequency Distributions. PSY 211 8-29-07. Frequency Distribution. Definition: Table/graph showing number of participants in each category. If I gave a 5-point quiz to a class, the distribution of scores might look like this:.

albert
Download Presentation

Frequency Distributions

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. Frequency Distributions PSY 211 8-29-07

  2. Frequency Distribution • Definition: Table/graph showing number of participants in each category

  3. If I gave a 5-point quiz to a class, the distribution of scores might look like this:

  4. Find the proportion (p) of people who have each score. p = f / N

  5. Find the percentage (%) of people who have each score. % = p * 100

  6. If the scores are spread out, it is okay to group them into a range of scores Some data: 96, 68, 74, 82, 86, 51, 66, 82, 91, 85, 77,89,88,88,61,90, 79,86,80,92,88,69, 44,99,81,82

  7. Turn a frequency table into a histogram: Scores

  8. Turn a frequency table into a histogram: f Scores

  9. Histogram of Quiz Scores f Scores

  10. Now turn that histogram (bar graph) into a polygon (shape, line graph) Polygon of Quiz Scores f 6 Scores

  11. You could graph relative frequencies (percentages) instead of frequencies % Scores

  12. Relative Histogram of Quiz Scores % Scores

  13. Distribution Shape • Rather than graph an entire distribution, sometimes researchers just describe its shape and provide a few statistics f x

  14. f Symmetrical distributions: look the same on both sides, mirror images x f x

  15. Positive Skew *Skewed distribution: lopsided, have a tail off to one side Tail indicates the direction of the skew (+ or -) f x Negative Skew f x

  16. Negative Skew In actuality, frequency polygons look more like these f x f Symmetrical x

  17. Percentile Rank • Used to describe where a score falls in a given distribution 95th percentile 50th percentile f f x x

  18. Finding Percentile Ranks cf = cumulative frequency, number of people with that score or lower

  19. Finding Percentile Ranks c% = cumulative percentage or percentile rank, percent with that score or lower

More Related