1. Introduction to Summary Statistics
Introduction to Engineering Design
Unit 3 – Measurement and Statistics
Introduction to Summary Statistics
Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

2. Introduction to Summary Statistics
The collection, organizing, calculating, evaluation, and interpretation of data
Statistical analysis of measurements can help verify the quality of a design or process

3. Introduction to Summary Statistics
Central Tendency
“Center” of a distribution
Mean, median, mode
Variation
Spread of values around the center
Range, standard deviation, interquartile range
Distribution
Summary of the frequency of values
Frequency tables, histograms, normal distribution, dot plots

4. Introduction to Summary Statistics
Mean Central Tendency
The mean is the sum of the values of a set of data divided by the number of values in that data set.
=μ = x i N

5. Introduction to Summary Statistics
Mean Central Tendency
=μ = x i N
μ = mean value
xi = individual data value
x i = summation of all data values
N = # of data values in the data set

6. Introduction to Summary Statistics
Mean Central Tendency
Data Set
Sum of the values = 243
Number of values = 11
μ = x i N
243
Mean = = = 11

7. Introduction to Summary Statistics
A Note about Rounding in Statistics
General Rule: Don’t round until the final answer
If you are writing intermediate results don’t round until the end
Mean – round to one more decimal place than the original data

8. Introduction to Summary Statistics
Mean – Rounding
Data Set
Sum of the values = 243
Number of values = 11
Reported: Mean =
μ = x i N
243
Mean = =
22. 09 = 11
22.1

9. Introduction to Summary Statistics
Mode Central Tendency
Measure of central tendency
The most frequently occurring value in a set of data is the mode
Symbol is M
Data Set:

10. Introduction to Summary Statistics
Mode Central Tendency
The most frequently occurring value in a set of data is the mode
Data Set:
Mode = M = 21

11. Introduction to Summary Statistics
Mode Central Tendency
The most frequently occurring value in a set of data is the mode
Unimodal: One mode
Bimodal: Two modes
Multimodal: More than two Modes
No mode: no data value is repeated

12. Introduction to Summary Statistics
Mode Central Tendency
Determine the mode of
48, 48 63, 62, 63, 49, 58, 2, 63, 5, 60, 59, 55
Mode = 63, unimodal
Determine the mode of
48, 63, 62, 59, 58, 2, 63, 5, 60, 59, 55
Mode = 63 & 59 Bimodal
Determine the mode of
48, 63, 62, 59, 48, 2, 63, 5, 60, 59, 55
Mode = 63, 59, & Multimodal

13. Introduction to Summary Statistics
Mode
Determine the mode of
1, 2, 4, 5, 6, 7
No mode

14. Median Central Tendency
Introduction to Summary Statistics
Median Central Tendency
Measure of central tendency
The median is the value that occurs in the middle of a set of data that has been arranged in numerical order
Symbol is x, pronounced “x-tilde” ~

15. Median Central Tendency
Introduction to Summary Statistics
Median Central Tendency
The median is the value that occurs in the middle of a set of data that has been arranged in numerical order
Data Set:

16. Median Central Tendency
Introduction to Summary Statistics
Median Central Tendency
A data set that contains an odd number of values always has a Median
Data Set:

17. Median Central Tendency
Introduction to Summary Statistics
Median Central Tendency
For a data set that contains an even number of values, the two middle values are averaged with the result being the Median
Middle of data set
Data Set:

18. Introduction to Summary Statistics
Range Variation
Measure of data variation
The range is the difference between the largest and smallest values that occur in a set of data
Symbol is R
Data Set:
Range = R = maximum value – minimum value
R = 44 – 3 = 41

19. Dot plot Distribution Create a dot plot for the data below
First pick your starting value and your scale. I decided to start at 0 and scale by 5. You do not have to start with 0 or scale by 5.

20. Introduction to Summary Statistics
Dot Plot Distribution 3 -1 -3 3 2 1 -1 -1 2 1 1 -1 -2 1 2 1 -2 -4 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6