Frequency Distributions

1
Frequency Distributions

• Organizing data in some comprehensible form so as
  to recognize trends and communicate meaningful
  information to others

2
Concepts

• What is a frequency distribution?
• What purpose does it serve?
• How would you organize the following data?

3
Frequency Distributions Tables
4
Some tips about Frequency Dist Tables
5
Frequency Distribution Histogram

• How would you represent this distribution
  graphically?
• Switch to Adobe slide Fig 2.2
• What if a set of data covers a wide range of
  values? What would be a practical way to
  organize such data?

6
Rules for creating grouped freq dist tables
7
Cumulative Frequency, Percentiles and Percentile
Rank
8
Other graphs

• Show slides 2.3-2.5

9
Smooth curves

• If data were collected for the entire population,
  or if samples were repeatedly drawn from a
  population over and over again and scores were
  recorded, the curve of the polygon will become
  smooth.
• This curve is called a bell-curve.
• Such a curve is assumed to be normal (i.e.,
  symmetrical distribution of scores).
• In a skewed distribution, the scores tend to
  pile up toward one end of the scale and taper off
  gradually at the other end.

10
Different shapes of distributions curves

• Fig 2.9

11
Stem-and-leaf display
12
Examples of interpolation
13
Rules for Interpolating
14
Visual Aid for Interpolation Example