Chapter 2: Organizing Data
2.1 – Frequency Distributions, Histograms,
and Related Topics
2.2 – Bar Graphs, Circle Graphs, and TimeSeries Graphs
2.3 – Stem-and-Leaf Displays
Focus Problem
“Say It With Pictures”
• Read page 33 in text book
• After this Chapter we will be able to…
– Explain what a histogram is and when to use it
– Differentiate common distribution shapes
– Select appropriate graphs for given data sets
– Order data and reveal distribution shape.
2.1 – Frequency Distributions,
Histograms, and Related Topics
Vocabulary
• Frequency Table
• Constructing a Frequency Table
1.
2.
3.
4.
5.
6.
Decide how many classes you want
Find class width
Determine data range for each class
Tally data and find frequency
Find the midpoint for each class
Determine class boundaries
Constructing a Frequency Table
1. Decide how many classes you want
– 5-15 classes
2. Find Class Width
largest data value – smallest data value
Desired # of classes
(Round up to whole number)
Constructing a Frequency Table
3. Determine data range for each class
– Lower class limit:
– Upper class limit:
4. Tally data and find frequency
– Tally
– Frequency
Constructing a Frequency Table
5. Find Midpoint (class mark) of each class
Lower class limit + upper class limit
2
6. Determine class boundaries (for graph)
– Upper class boundary:
– Lower class boundary:
7. (Extra) Find Relative Frequency (%)
Class frequency
Total of all frequencies
Lets put it all together…
Nurses on the eighth floor of Community Hospital believe they
need extra staffing at night. To estimate the night workload, a
random sample of 35 nights was used. For each night, the total
number of room calls to the nurses station on the eights floor
was recorded as follows:
68 60 69 71 83 58 90 86 71 71 92 95 70
46 74 18 84 82 75 63 101 77 102 80 86 85
73 86 62 100 90 37 88 70 87
Histograms and
Relative-Frequency Histograms
Procedure:
1. Make a frequency table
2. Place class boundaries on horizontal axis and
frequencies/relative frequencies on vertical
axis
3. Draw bars (touching)
Histograms and
Relative-Frequency Histograms
Histogram
Relative-Frequency Histogram
Histograms and
Relative-Frequency Histograms
Distribution Shapes
• Symmetrical:
• Uniform/Rectangular:
• Skewed Left / Skewed Right (Tails):
• Bimodal:
Guided Exercise #1 (if time)
• With table partners, turn to page 40-41
– Cover answers
– Discuss answers
• Check
– Whole group clarification
Checkpoint
Organize raw data using a frequency table
Construct histograms and relative frequency
histograms
Recognize basic distribution shapes:
Uniform
Symmetric
Skewed
Bimodal
Interpret graphs in the context of the data
setting
Homework
• Read Pages 34-42
– Take notes on what we have not covered
• Do Problems
– Page 43-47 (1-10) try 11-13 (dotplots)
• Not multiple choice!
• Check odds in back of book
• Read and preload 2.2 information
– Notes/vocab