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Final

# Ch5 Quantitative Data, Displaying and Describing.pdf

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University of Maryland

Business and Management

BMGT 230

Kazim Ruhi

Spring

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Ch5 Quantitative Data, Displaying and Describing
Friday,February 7,2014
11:56 AM
Two graphs: histogram & stem-and-leaf plot
note for steam-and-leaf plot
•
left side: bins,right side: "bars"
• bars can be 0.0-0.5,do not have to always be 1
Building a Frequency Table:▯
Continuous Data
1. Determine the number of categories (classes/bins)
a. General Guidelines
2. Establish class width
a. Minimum width is the range of the data
i. Largest data point–Smallest data point = Range 3. Set the class boundaries
4. Determine the frequency in each class
a. Count the number of data points in each category
Frequency Histogram
-Visual representation of the frequency table
• The classes/intervals/bins are shown on the horizontal axis
• Frequency is measured on the vertical axis
Example: 12,13,17,21,24,24,26,27,27,30,32,35,37,38,41,43,44,46,53,58
5. Sort raw data from low to high (already done)
6. Find range: 58-12 = 46
7. Select number of classes: 5 (usually between 5 and 20)
8.
Compute class width: 10 (46/5 then round off)
9. Determine class boundaries: 10,20,30,40,50
10. Count the number of values in each class
▯
▯
Shape of a distribution
Mode: usually the single,most frequent value • one hump: unimodal
•
two humps: bimodal
• three or more humps: multimodal
• a distribution does not seem to have any mode,all bars approximately same height: uniform
Symmetry
• symmetric: mirror image
• tails: the thinner ends of a distribution
• skewed: one tail stretches out farther than the other Outlier
-Data points that don’t seem to ﬁt in the distribution.
• They should be understood in the context of the data.An outlier for a year of data may not
be an outlier for the month in which it occurred and vice versa.
• They should be investigated to determine if they are in error.The values may have simply
been entered incorrectly.If a value

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