Business 90: Business Statistics

1
Business 90 Business Statistics Professor
David Mease Sec 03, T R 730-845AM BBC 204
Lecture 4 More of Chapter Presenting Data in
Tables and Charts (PDITAC) Agenda 1) Go
over Quiz on Homework 1 2) Assign Homework 2 (due
Tuesday 2/16) 3) Announcement no office hours
today (2/4) 4) Lecture over more of Chapter PDITAC
2
Homework 2 - Due Tuesday 2/16

• 1) Read the chapter entitled Presenting Data in
  Tables and Charts
• 2) The Excel file at http//www.cob.sjsu.edu/mease
  _d/old-quiz-scores.xls has Quiz 1 scores for a
  Bus 90 class I thought last semester. Right click
  this link and select "Save Target As..." to
  download this file onto your computer. Then open
  it using Excel.
• a) Make the frequency distribution by hand. Begin
  at 0 and end at 22 using 11 intervals. (Hint You
  may use Excel to sort the data first if you
  like).
• b) Graph the frequency histogram by hand.
• c) Graph the percentage polygon by hand.
• d) Make the cumulative percentage distribution by
  hand.
• e) Graph the ogive by hand.
• f) Check your answer for part a using Excel.
• 3) The data at http//www.cob.sjsu.edu/mease_d/hou
  ses.xls has house prices for a sample of 1500
  California homes. The prices are in thousands of
  dollars. Right click this link and select "Save
  Target As..." to download this file onto your
  computer. Then open it with Excel and use Excel
  to do the following. Be sure to print out your
  solutions and bring them with you to class for
  the quiz.
• a) Make the frequency distribution using Excel.
  Begin at 0 and end at 3.5 million using 7
  intervals.
• b) Graph the percentage histogram using Excel.
• c) Graph the percentage polygon using Excel.
• d) Make the cumulative percentage distribution
  using Excel.
• e) Graph the ogive using Excel.

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Announcement

• Today (2/4) I will not have office hours. If
  you need to talk to me please email me or call
  (419-944-9652).

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Statistics for Managers Using Microsoft Excel
4th Edition

• Presenting Data in Tables and Charts

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Chapter Goals

• After completing this chapter, you should be able
  to
• Create an ordered array
• Construct and interpret a frequency distribution,
  histogram, and polygon for numerical data
• Construct and interpret a cumulative percentage
  distribution and ogive for numerical data
• Create and interpret contingency tables, bar
  charts, and pie charts for categorical data
• Create and interpret a scatter diagram and a
  least squares regression line (in other chapter
  p. 387-398)
• Describe appropriate and inappropriate ways to
  display data graphically

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Example
Below are Bus 90 midterm exam scores. Describe
this data.
92 60 83 36 62 65 80 88 50 63 92 64 84 89 83 80 8
8 91 90 84 71 77 25 92 49 88 54 51 59 41 71 53 69
68 68 57 60 90 66 50

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In class exercise 5 Construct a frequency
distribution for the exam scores beginning at 20
and ending at 100 using 8 intervals.
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Graphing Numerical Data The Histogram

• A graph of the data in a frequency distribution
  is called a histogram
• The class boundaries (or class midpoints) are
  shown on the horizontal axis
• the vertical axis is either frequency or
  percentage
• Bars of the appropriate heights are used to
  represent the number of observations within each
  class

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In class exercise 6 Construct a frequency
histogram for the exam scores.
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In class exercise 7 Could I use frequency
histograms to compare exam scores for two
different classes?
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In class exercise 8 Construct a percentage
distribution for the exam scores.
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In class exercise 9 Construct a percentage
histogram for the exam scores.
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Frequency Distributions in Excel
In ICE 5 we constructed a frequency
distribution for the exam scores. 92 60 83 36 62
65 80 88 50 63 92 64 84 89 83 80 88 91 90 84 71 7
7 25 92 49 88 54 51 59 41 71 53 69 68 68 57 60 90
66 50 Next we will learn how to make frequency
distributions using Microsoft Excel. This is
especially useful for large data sets.
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Frequency Distributions in Excel
1) First make a column with your desired upper
end points for your intervals. 2) Next
highlight a column (of the same length) to store
the frequency values. 3) Do insert gt function
gt statistical gt frequency. 4) Data_array is
the data and Bins_array is your desired upper
end points for your intervals. 5) IMPORTANT
You must hold down shift and control keys then
press enter.
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Frequency Distributions in Excel
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Frequency Distributions in Excel
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Frequency Distributions in Excel
18
In class exercise 10 Construct a frequency
distribution for the exam scores using Excel.
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Frequency Distributions in Excel
Problem We do up to but not including but
excel doesnt do this. Solution Change 30 to
29.99 and change 40 to 39.99 and so on. But you
dont want it to say 29.99 when you make your
table. Solution Paste table somewhere else and
then fix the numbers.
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In class exercise 10 Construct a frequency
distribution for the exam scores using
Excel. ANSWER
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In class exercise 11 Construct a percentage
distribution for the exam scores using Excel.
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In class exercise 11 Construct a percentage
distribution for the exam scores using
Excel. ANSWER
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Histograms in Excel
1) You first need one column with the class
MIDPOINTS and another column that has the
frequencies. 2) Do insert gt chart gt column.
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Histograms in Excel
3) Click Next and put your frequencies in the
Data range and then click the series tab at
the top and put your midpoints in the Category
(X) axis labels 4) Add axis labels and a
title, remove the legend and then click
Finish
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Histograms in Excel
5) IMPORTANT Histograms do not have gaps.
Correct this by double clicking on any bar, go to
Options and make the Gap width be 0.
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In class exercise 12 Construct a frequency
histogram for the exam scores using Excel.
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In class exercise 12 Construct a frequency
histogram for the exam scores using
Excel. ANSWER
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In class exercise 13 Construct a percentage
histogram for the exam scores using Excel.
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In class exercise 13 Construct a percentage
histogram for the exam scores using
Excel. ANSWER
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Questions for Grouping Data into Classes

• 1. How wide should each interval be? (How
  many classes should be used?)
• 2. How should the endpoints of the intervals
  be determined?
• Often answered by trial and error, subject to
  user judgment
• The goal is to create a distribution that is
  neither too "jagged" nor too "blocky
• Goal is to appropriately show the pattern of
  variation in the data

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How Many Class Intervals?

• Too Many (Narrow class intervals)
• may yield a very jagged distribution with gaps
  from empty classes
• Can give a poor indication of how frequency
  varies across classes
• Too Few (Wide class intervals)
• may compress variation too much and yield a
  blocky distribution
• can obscure important patterns of variation.