How to build frequency tables

1
How to build frequency tables

• For Categorical and
• Numerical data

2
Frequency Tables Categorical

• Rows are called classes
• Each categorical (discrete) value occupies its
  own class
• Then frequency is counted for each class in
  absolute () and in relative () terms.

3
Example

• Variable Gender
• Nature Categorical, Nominal.
• Values Male, Female
• Raw Data M, M, F, M, M, F, F, F, F, F, M, M, F,
  F, F, F, M, M, F, F

4
Gender Frequency Distribution
5
Frequency Tables Numerical

• Rows are called classes
• The number of classes, c, is a function of the
  number of observations, n
• C 1 3.3LOG(n) Sturges law
• If n 50, then c 6.6

6
Frequency Tables Numerical

• Each class consists of a range of values know as
  the class width, w.
• The class width must be the same for all classes.
• W Range c, where Range MAX-MIN
• If MIN 82 and MAX 213 for n50 observations,
  then
• W (213 82) / 6.6 20

7
Frequency Tables Lower Class Limits

• To build classes, we then start measuring class
  widths FROM a nice (round) number smaller than
  MIN.
• The LOWER CLASS LIMITS are c numbers that are 1
  class width, w, greater than the previous one.

8
Frequency Tables Upper Class Limits

• UPPER CLASS LIMITS mark ending values for each
  class.
• They are smaller in value than the LOWER CLASS
  LIMITS of the previous classes.

9
Frequency Tables Value Classes Example

• Frequency Table Class Limits

• Example 2.12 on page 57, UTILITY
• Data n50, MIN82, MAX213
• Range 213 82 131
• C 1 3.3LOG(50) 7
• W 131 / 7 20

10
Frequency Table absolute and counts

• To complete a frequency table we then tally how
  many observations in a data set fall in each of
  the previously formed class ranges.
• These tallies can be accounted for in units or in
  of the total number of observations, n.

11
Frequency Table
12
Frequency Tables using PhStat

• To count frequencies, all you do is let PhStat do
  the tallying for you, using the command sequence
• PhStat
• Descriptive Statistics
• Frequency Distribution
• Then, you input the proper cell ranges in the
  dialog box for the procedure
• Variable cell range range of cells for data.
• Bins cell range class limits for classifying
  data.