Chapter 12
Analyzing the Results of Research Investigations
- Comparing Group Percentages
o (Example page 224) Calculate percentage of Fs who like to travel compared to Ms that like to travel
o Out of 50 Fs and 50 Ms, say 40 Fs and 30 MS like travelling, therefore, 80% Fs like to travel and 60% Ms
- Correlating Individual Scores
o Do not have distinct groups of subjects, individuals measured on 2 variables (each with range of numerical values)
- Comparing Group Means
o (Example page 225) Comparing mean number of aggressive acts by children in 2 conditions (model and control) to determine
whether child who observed model were more aggressive than children in control condition
Frequency Distributions
- Indicates number of individuals that receive each possible score on variable
- Graphing Frequency Distributions
o Pie Charts - divide a whole circle in “slices” that represent relative percentages, particularly useful when representing nominal scale
information, frequently used in applied research
o Bar Graphs – use separate and distinct bar for each piece of info with x- and y-axis, length of each bar represents number of people
who responded with specific choice
o Frequency Polygons – use line to represent frequencies, most useful when data represent interval or ratio scales
o Histograms – uses bars to display frequency distribution for quantitative variable
Descriptive Statistics
- Allow researchers to make precise statements about data, 2 statistics needed – single number used to describe central tendency, another number
describes variability
- Central Tendency – tells us hat the sample as a whole, or on average, is like. Mean (set of scores obtained by adding all scores and dividing by
number of scores – only for interval or ratio scales), median (score that divides the group in half - ordinal scale) and mode (most frequent score
– only for nominal scales, does not use actual values on scale but simply indicates most frequently occurring value)
- Variability – number that characterizes the amount of spread in a distribution of scores. Standard deviation (indicates average deviation of
scores from mean), variance (standard deviation is square root of variance), range (difference between highest and lowest score). Standard
deviation larger when more people have scores further from mean.
Graphing Relationships
- Common – bar or line graph
- Independent variable on x-axis, dependent variable on y-axis
- Bar graphs used when values on x-axis are nominal categories, line graphs used when values on x-axis are numeric
Correlation Coefficients: Describing the Strength of Relationships
- Correlation coefficient – statistic that descri

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