Appendix B: Statistical Methods

Statistical Methods: Graphing Data

• Frequency distribution• Histogram• Frequency polygon

Figure B.1 Graphing data

Descriptive Statistics

• Measures of Central Tendency• Mean• Median• Mode• Skewed Distributions• Negative/Positive• Measuring Variability• Standard Deviation

Figure B.2 Measures of central tendency

Figure B.3 Measures of central tendency in skewed distributions

Figure B.4 The standard deviation and dispersion of data

Figure B.5 Steps in calculating the standard deviation

The Normal Distribution

• Psychological tests– Relative measures– Standard deviation the unit of measure

• Conversion to percentile scores

Figure B.6 The normal distribution

Figure B.7 The normal distribution and SAT scores

Measuring Correlation

• Correlation coefficient– Positive = direct relationship– Negative = inverse relationship

• Magnitude: 0 to plus/minus 1• Scatter diagrams• Correlation of determination

Figure B.8 Scatter diagrams of positive and negative correlations

Figure B.9 Scatter diagram of the correlation between TV viewing and SAT scores

Figure B.10 Computing a correlation coefficient

Figure B.11 Correlation and the coefficient of determination

Hypothesis Testing

• Inferential statistics• Sample• Population• Null hypothesis vs. research hypothesis• Statistical significance

Figure B.12 The relationship between the population and the sample