Psyc 321_04 numerical description
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This document discusses numerical description in developmental research methods. It describes different types of scales used to measure variables, including nominal, ordinal, interval, and ratio scales. It also discusses distributions, measures of central tendency (mean, median, mode), variation (range, variance, standard deviation), standard scores, correlation, and examples of positive, negative and no correlation.
Psyc 321_04 numerical description
- 1. Developmental Research Methods Topic 4: Numerical Description 10/1/2014 CEDP321 Ryan Sain, Ph.D. 1
- 2. Properties of Scales • Measuring Variables – Personality; IQ, etc • Magnitude – Size, Quantity • Equal intervals – Equal distance between points in terms of concept • Absolute zero – This is nothing. Noting of the property being measured exists. 10/1/2014 CEDP321 Ryan Sain, Ph.D. 2
- 3. Scales of Measurement • Nominal – Mutually exclusive categories • Ordinal – Order of the numbers mean something The scale you are using – determines what types of statistics you can do on the data! – Magnitude – but no zero point and no equal intervals • Interval – Magnitude – Equal intervals – No absolute zero • Ratio – Equal intervals and a true zero point and magnitude 10/1/2014 CEDP321 Ryan Sain, Ph.D. 3
- 4. Distributions Allow you to see how your data looks ◦ Ranges or bins (class interval) ◦ 10 or 20 ranges to cover the entire data set You can see how skewed the data is Allows you to decide what stat to use 10/1/2014 CEDP321 Ryan Sain, Ph.D. 4
- 5. Distributions Mean Alcohol Consumption by Age 10/1/2014 CEDP321 Ryan Sain, Ph.D. 5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 5 to 10 11 to 15 16 to 20 21 to 25 26 to 30 31 to 35 36 to 40 Average Drinks per Week Age mean alcohol consumption
- 6. Distributions - Skew mean alcohol consumption 10/1/2014 CEDP321 Ryan Sain, Ph.D. 6 6 5 4 3 2 1 0 5 to 10 11 to 15 16 to 20 21 to 25 26 to 30 31 to 35 36 to 40 mean alcohol consumption
- 7. Measures of central tendency Mean Median ◦ Insensitive to extreme scores mode 10/1/2014 CEDP321 Ryan Sain, Ph.D. 7
- 8. Variation Variability in your data Range Sum of the Squared Deviations from the Mean 10/1/2014 CEDP321 Ryan Sain, Ph.D. 8
- 9. Variance and Standard Deviation Variance Standard Deviation or 10/1/2014 CEDP321 Ryan Sain, Ph.D. 9
- 10. Standard scores Z score 10/1/2014 CEDP321 Ryan Sain, Ph.D. 10
- 11. Correlation Relationship between two variables No causation! 10/1/2014 CEDP321 Ryan Sain, Ph.D. 11
- 12. Positive Correlation 10/1/2014 CEDP321 Ryan Sain, Ph.D. 12
- 13. Negative Correlation 10/1/2014 CEDP321 Ryan Sain, Ph.D. 13
- 14. No correlation 10/1/2014 CEDP321 Ryan Sain, Ph.D. 14