Week 1 Day 3 (2.1, 2.2, 2.3) Summarizing Data I

Step one You will need to determine the type of the variable to summarize, whether it is Qualitative or Quantitative, since different types of variables requires different ways of summarization and different interpretations.

Some Resources 1. Textbook. Appendix 2.2, page

Summarizing Qualitative Data Frequency Distribution Relative Percent Frequency Bar Graphs/Charts Pie Charts

Frequency Distribution Excel Function for Frequency Distribution =COUNTIF(range, criteria). Example: =COUNTIF(D2:D16,E2:E4) 1. Create two additional columns: Label and Frequency 2. Fill out the column “Label” by hand 3. Use countif to calculate frequency.

Frequency Distribution To Get Percentage (Relative Frequency) 1. Calculate total (assume it is in cell E8) 2. Set up a new column using the function Example: =E2/$E$8

Bar Graphs and Pie Charts 1. Highlight the “Label” and “Frequency” columns 2. To get a bar graph: Insert  Charts  Column  2-D Column  Clustered Column 3. To get a pie chart: Insert  Charts  Pie  2-Pie

Example of Bar Graph and Pie Chart Bar Graph Pie Chart

Summarizing Quantitative Data Making classes (width of interval) Relative Frequency/% frequency Dot plot Stem and Leaf Plots Histograms Cumulative Distribution

Create a Frequency Table 1.Have to decide the width of interval first!!! 2.Make a frequency table i. Create three new columns “range”, “upper Limit” and “frequency” ii. Enter range and upper limit from step 1. iii. In the frequency column, use the function FREQUENCY(data array, bins array)

Some Important Tips i.Type, don’t enter, frequency ii.Use ctrl+shift+enter to finish iii. The percentage is calculated the same way as the qualitative data

Dot Plot and Histogram 1. Highlight the “range” column, press “ctrl” and then also highlight the “frequency” column. 2. For Histogram: Insert  Charts  Column  2-D Column  Clustered Column 3. For Dot Plots: Insert  Charts  Scatter  Scatter with only markers

Edit Plots You can edit the plots/graphs you generate. For example, add titles, numbers, etc. This can be done in excel by clicking the Chart Layouts group  More  Choose corresponding layout  edit titles etc.

Cumulative Frequency and Percentage Cumulative Frequency: 1. Set up a new column and name it “cum. Freq” 2. Next entry = Previous entry + the corresponding cell in the frequency column Cumulative Percentage: Same as percentage frequency