1. Frequency Distribution 2011, 9, 22

2. Lecture Topics  Frequency distribution table*  Frequency distribution graphs*  Shape of a distribution

3. Need Your  Number of out-of-state trips in last 12 months?  Distribution of a variable: A summary of all the different values of a variable  Descriptive statistics: Statistical tools/procedures to help organize, summarize, and simplify a large set of data

4. Frequency Distribution Table Frequency Distribution Table Value – X (n=20) 10 9 8 7 6 5 4Tallyll llll llll ll lll ll l lFrequency (f) 2 4 7 3 2 1 1 Proportion (P =f/n).1.20.35.15.1.05.05 Percentage (%= px100) 10% 20% 35% 15% 10% 5% 5%5%5%5% Cumulative % (c% ) 100% 90% 70% 35% 20% 10% 5%

5. Your Turn…

6. Frequency Distribution Table (n = 30) Class Interval fp%c% A (90-100) 7.2424%100% B (80-89) 18.6060%76.5% C (70-79) 4.1313%16.5% D (60-69) 1.033%3.2% Xfp%c% 1001.0323.2%100.0 971.0323.2%96.0 952.0676.7%92.8 942.0676.7%86.1 901.0323.2%79.4 884.13313.3%76.2 851.0323.2%62.9 839.30030%59.7 814.13313.3%29.7 751.0323.2%16.4 703.10010%13.2 651.0323.2%3.2 Grouped Frequency Distribution Table

7. Frequency Distribution Graphs Line Graph  All start with 2 perpendicular lines called axes –Horizontal line: The X-axis indicates values (scores) –Vertical line: The Y-axis indicates frequencies

8.  Histogram: A bar type graph for continuous data. No gaps between adjacent bars  Bar Graph: A bar-type graph for discrete variable. Gaps between adjacent bars. Outlier

9. Copyright © 2002 Wadsworth Group. Wadsworth is an imprint of the Wadsworth Group, a division of Thomson Learning Shape of a Distribution

10. Lecture Recap: Frequency Distribution  What is a distribution? What is descriptive statistics?  Table –Frequency distribution table –Grouped frequency distribution table  Graphs –Line graph –Histogram vs. Bar chart –Outliers  Shape of a distribution –Symmetrical –Positively skewed –Negatively skewed