Introducing Communication Research 2e © 2014 SAGE Publications

Chapter SixSummarizing Research Results: Data Reduction and Descriptive Statistics.

Key Concepts

•Categorical vs. continuous data.

•Mean, median, mode.

•Frequency.

•Minimum, maximum, range.

•Variance, standard deviation, z-score.

•Normal curve.

•Chi-square test.

Introducing Communication Research 2e © 2014 SAGE Publications

Measures of Central Tendency

•Mean:Add scores; divide total by number of

scores.•Mode

Most frequent score.•Median

▫Middle score of ranked scores if number of scores is uneven.

▫1/2 way between two middle scores if number of scores is even.

Introducing Communication Research 2e © 2014 SAGE Publications

Frequency Table

•Shows number or frequency of scores e.g -

Hours per week

TV Viewing

Number of people

%

0-9 2 6.6

10-19 8 26.7

20-29 12 40.0

30-39 6 20.0

40 or more 2 6.6

30 100

Introducing Communication Research 2e © 2014 SAGE Publications

Contingency Table

•Shows how one variable changes with another e.g. TV viewing by gender.

Hours per week

TV Viewing

Male Female

0-9 2 0

10-19 6 2

20-29 4 8

30-39 4 2

40 or more 0 2

16 14

Introducing Communication Research 2e © 2014 SAGE Publications

Measures of Dispersion

•Maximum

•Minimum

•Maximum - minimum = range

•Variance

•Standard Deviation = square root of variance

Introducing Communication Research 2e © 2014 SAGE Publications

Two Important Calculations

•z-Score▫Standardizes scores to allow comparison

of different variables.

•Chi-square ▫Assesses difference between groups’

distributions of scores.

Introducing Communication Research 2e © 2014 SAGE Publications

Chapter Summary•Descriptive statistics -

▫describe and summarize data•Measures of Central Tendency

▫mean, median, mode•Measures of Dispersion

▫minimum, maximum, range, variance, standard deviation

•Chi-square test▫Compares distributions of scores for two

or more groups.

Introducing Communication Research 2e © 2014 SAGE Publications

Vocabulary Review

Introducing Communication Research 2e © 2014 SAGE Publications

Web Resources

Chi-square Calculators

• http://www.physics.csbsju.edu/stats/chi-square_form.html

• http://graphpad.com/quickcalcs/chisquared1.cfm

Introducing Communication Research 2e © 2014 SAGE Publications