Frequency distributions

1
Frequency distributions

• Chapter 2

2
What are frequency distributions?

• Table or graph that lets you quickly and easily
  see how many responses of a particular value (or
  range of values) you have

3
Why do we care?

• Lets you quickly and easily see if you have
  invalid values
• Lets you quickly and easily see where
  participants are
• Consistent with who recruited e.g., if
  newlyweds, should have high levels of
  satisfaction, and short levels of length of
  marriage

4
Table

• One column has possible values of variable,
  grouped or ungrouped
• Another has number of people with that value (or
  range of values)
• Another may have percentage or proportion of
  people with that value (or range of values)

5
Graphs

• Regardless of type of frequency distribution
  graph
• Value of variable on X axis
• Frequency of that value on Y axis

6
Histogram

• Used for quantitative variable
• Bar for each possible value of variable
• No space between bars
• Height of bar number of people with that value

7
Bar graph

• Same idea as histogram, but used for qualitative
  variables
• To reinforce this, space between bars on graph

8
Polygon

• Think of shape created from dots and connecting
  lines
• Dot placed at height corresponding to number of
  people with a particular value
• Repeated for each possible value
• Dots connected

9
Types of distributions

• Symmetrical
• Skewed
• Positive/to the right
• Negative/to the left
• Named by where the tail is