Frequency distributions l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 19

Frequency Distributions PowerPoint PPT Presentation


  • 183 Views
  • Updated On :
  • Presentation posted in: General

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:.

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Frequency distributions l.jpg

Frequency Distributions

PSY 211

8-29-07


Frequency distribution l.jpg

Frequency Distribution

  • Definition: Table/graph showing number of participants in each category


Slide3 l.jpg

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


Slide4 l.jpg

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


Slide5 l.jpg

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


Slide6 l.jpg

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


Slide7 l.jpg

Turn a frequency table into a histogram:

Scores


Slide8 l.jpg

Turn a frequency table into a histogram:

f

Scores


Slide9 l.jpg

Histogram of Quiz Scores

f

Scores


Slide10 l.jpg

Now turn that histogram (bar graph) into a polygon (shape, line graph)

Polygon of Quiz Scores

f

6

Scores


Slide11 l.jpg

You could graph relative frequencies (percentages) instead of frequencies

%

Scores


Slide12 l.jpg

Relative Histogram of Quiz Scores

%

Scores


Distribution shape l.jpg

Distribution Shape

  • Rather than graph an entire distribution, sometimes researchers just describe its shape and provide a few statistics

f

x


Slide14 l.jpg

f

Symmetrical distributions: look the same on both sides, mirror images

x

f

x


Slide15 l.jpg

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


Slide16 l.jpg

Negative Skew

In actuality, frequency polygons look more like these

f

x

f

Symmetrical

x


Percentile rank l.jpg

Percentile Rank

  • Used to describe where a score falls in a given distribution

95th percentile

50th percentile

f

f

x

x


Finding percentile ranks l.jpg

Finding Percentile Ranks

cf = cumulative frequency, number of people with that score or lower


Finding percentile ranks19 l.jpg

Finding Percentile Ranks

c% = cumulative percentage or percentile rank, percent with that score or lower


  • Login