Quantitative Research Methods Chapter 2

1
Quantitative Research MethodsChapter 2

• Excerpts from Hinkle, D. E., Wiersma, W., and
  Jurs, S. G. (2003) Applied Statistics for the
  Behavioral Sciences. Boston, MA Houghton Mifflin
  Company.

2
Coding Data

• The process of coding data involves assigning
  numerical values to nonnumeric categories of a
  variable.

3
Data File

• In a data file, each row contains the data
  record for a single subject, and the columns
  contain the data for the variables. (p. 19)

4
A Spreadsheet

• A spreadsheet is a two-dimensional array of
  cells. For the purpose of data entry, the rows of
  the spreadsheet represent the data lines of the
  participants. The columns of the spreadsheet
  represent the variables to be included in the
  data record. (p.19)

5
Stem-and-Leaf Displays
Stem-and-Leaf displays are one useful strategy
for exploring distributions of data. This was
developed by Tukey (1977). (p.21)
The first step in developing stem-and-leaf
displays is to determine the stem. In this
example, we use the tens digit for the stem,
that is 990, 880, 770, etc. The leaves for the
display are the units digit. (pp. 21-22)

• 9 1 3
• 8 0 1 2 4 4 4 7 7 8
• 7 1 1 2 2 4 1 9
• 6 2 7 8 8
• 5 1 2 3 3 4 5 7 9
• 4 1 2 2 3 5 7 9 9
• 3 1 4 4 6 8 8 9
• 2 2 4 8 8 9
• 1 6 8

6
Frequency Distribution

• A Frequency distribution is a tabulation that
  indicates the number of times a given score
  occurs. It is generally considered the first step
  in any data analysis for data sets too large for
  stem-and-leaf displays. (p. 22)

7
Class Interval

• The scores within any class interval are assumed
  to be uniformly distributed throughout the
  interval, and all are assumed to be adequately
  represented by the midpoint. (p. 26)

8
Exact Limits of Class Interval

• Exact limits of class intervals are based on the
  assumption that the variable under study is
  continuous, even though the measurement may be in
  whole numbers. (p. 25)

9
Three-Quarter High Rule

• There is a simple rule that helps ensure
  consistency and avoid distortion in graphs. It
  states that the height of the Y axis should be
  approximately three-quarters the length of the X
  axis so as not to misrepresent data. (p. 30)

10
Ogive

• The ogive is the graph of a cumulative frequency
  distribution. It is useful for determining the
  various percentile points in a distribution of
  scores. (p. 35)

11
Cumulative Frequency Distribution

• The cumulative frequency distribution is
  constructed by adding the frequency of scores in
  any class interval to the frequencies of all the
  class intervals below it on the scale of
  measurement. (p. 35)