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Statistical Methods

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Box-and-Whisker Plot. Graphical display of data using. 5-number summary. 1 - 28 ... Box-and-Whisker Plot. 1 - 29 1997 Prentice-Hall, Inc. Conclusion ... – PowerPoint PPT presentation

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Title: Statistical Methods


1
Statistical Methods
2
Descriptive Statistics
  • Involves
  • Collecting data
  • Presenting data
  • Characterizing data
  • Purpose
  • Describe data

3
Inferential Statistics
Population?
  • Involves
  • Estimation
  • Hypothesis testing
  • Purpose
  • Make decisions about population characteristics

4
Key Terms
  • Population (universe)
  • All items of interest
  • Sample
  • Portion of population
  • Parameter
  • Summary measure about population
  • Statistic
  • Summary measure about sample

5
Data Types
6
Data Type Examples
  • Numerical
  • Discrete
  • To how many magazines do you subscribe currently?
    ___ (Number)
  • Continuous
  • How tall are you? ___ (Inches)
  • Categorical
  • Do you own savings bonds? __ Yes __ No

7
How Are Data Measured?
  • Nominal scale
  • Ordinal scale
  • Interval scale
  • Ratio scale

8
Standard Notation
9
Numerical Data Properties
Central Tendency (Location)
Variation (Dispersion)
Shape
10
Numerical DataProperties Measures
11
Central Tendency
12
Mean
  • Measure of central tendency
  • Most common measure
  • Acts as balance point
  • Affected by extreme values (outliers)
  • Formula (sample mean)

13
Median
  • Measure of central tendency
  • Middle value in ordered sequence
  • If odd n, middle value of sequence
  • If even n, average of 2 middle values
  • Not affected by extreme values
  • Position of median in sequence

14
Mode
  • Measure of central tendency
  • Value that occurs most often
  • Not affected by extreme values
  • May be no mode or several modes
  • May be used for numerical categorical data

15
Quartiles
  • Measure of noncentral tendency
  • Split ordered data into 4 quarters

25
25
25
25
Q1
Q2
Q3
16
Summary of Central Tendency
17
Variation
18
Range
  • Measure of dispersion
  • Difference between largest smallest
    observations
  • Ignores how data are distributed

19
Interquartile Range
  • Measure of dispersion
  • Also called midspread
  • Spread in middle 50
  • Not affected by extreme values
  • Formula

20
Variance Standard Deviation
  • Measures of dispersion
  • Most common measures
  • Consider how data are distributed
  • Show variation about mean (X or m)

21
DISPERSION ABOUT THE MEAN
  • Variance
  • s2

22
DISPERSION ABOUT MEAN (cont.)
  • Standard deviation (sd)

s
23
PROPERTIES OF THE STANDARD DEVIATION IN A NORMAL
CURVE
1s 68
2s 95
3s 99
24
Summary of Variation Measures
25
Shape
26
Shape
  • Describes how data are distributed
  • Measures of shape
  • Skew Symmetry

27
Box-and-Whisker Plot
  • Graphical display of data using5-number summary

28
Shape Box-and-Whisker Plot
29
Conclusion
  • Explained numerical data properties
  • Described summary measures
  • Central tendency
  • Variation
  • Shape
  • Analyzed numerical data using summary measures

30
This Class...
Please take a moment to answer the following
questions in writing
  • What was the most important thing you learned in
    class today?
  • What do you still have questions about?
  • How can todays class be improved?
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