Research Results

Research Results

1. Frequency distributions

   • Indicates the number of participants who receive a score on a variable
   • Pie chart
   • Bar graph
     • Used to compare group means or percentages
   • Frequency polygons
     • Uses a line to represent frequencies
     • Used in interval or ratio scales
   • Histograms
     • Uses bars to display a frequency distribution for a quantitative variable

2. Descriptive statistics

   • Central tendency
     • Mean
       • X bar or M
     • Median
       • mdn
     • Mode
       • Good for nominal scales
     • Tells us what the sample as a whole is like
   • Variability
     • Characterizes the amount of spread in a distribution of scores
     • Standard deviation
       • The average deviation of scores from the mean
     • Variance
       • The standard deviation is derived from this
     • Range

3. Correlation coefficients

   • Statistic that describes how strongly variables are related
   • Pearson product moment correlation coefficient
     • Used when both variables have interval or ratio scale properties
     • Provides information about strength and direction
   • Restriction of range
     • When individuals in sample are similar
   • Can only find linear relationships

4. Effect size

   • Strength of association between variables
   • Squared correlation coefficient
     • The percent of shared variance between two variables
     • Correlation = .7, therefore % = 49%
   • Cohen's D
     • The magnitude of the effect of the independent variable on the dependent variable
   • Regression equations
     • Used to predict one's score when that person's score on another test is known
   • Multiple correlation
     • Combines predictor variables to increase the accuracy of a prediction
   • Partial correlation
     • Provides a way of statistically controlling third variables in non experiments