Basic Civil Engineering notes on Transportation Engineering & Modes of Transport
Descriptive Statistics and Interpretation ExampleQNT561 Ver.docx
1. Descriptive Statistics and Interpretation Example
QNT/561 Version 8
7
University of Phoenix Material
Descriptive Statistics and Interpretation Example
Interpretation Phrases
Central Tendency:
Mean = average of a set of data
Median = half or equal number of data is above and half or
equal number of data is below. It is a midpoint in an ordered
(sorted) set of data, a physical location
Mode = most frequent value in a set of data
Dispersion:
Standard deviation = variation
Interquartile range (IQR) = the middle 50% of the data
Range = the difference between the largest and smallest value
of the data
Confidence Interval: (data must be normal)
There is 95% confidence that the population average is between
_____ and ____ units.
Normal or significantly skewed data:
MegaStat: Descriptive statistics Normal curve goodness of fit p-
2. value
Normal, p-value > .05
Significantly Skewed, p-value < .05
Histogram: Eyeball the histogram.
Normal data will have a symmetrical or slightly skewed shape.
Significantly Skewed shape will have extreme skewness
Use phrase combinations: Normally distributed: Mean and
Standard Deviation, Not normally distributed: Median and IQR
Descriptive Statistics
Body Weight (Lbs.)
Central Tendency:
Mean = 149 Lbs.
Dispersion:
Standard deviation = 30 Lbs.
Count:
100
Min/Max:
99 pounds and 234 Lbs.
Confidence Interval:
144 to 155 Lbs.
See the histogram in Appendix A, and descriptive statistics in
Appendix B.
Age
Distribution is not normally distributed
Central Tendency:
Median = 36 years
Dispersion:
3. Interquartile Range = 20.5 years / 2 = ± 10 years
Count:
100
Min/Max:
18 years and 74 years
Confidence Interval:
Not applicable (data is not normally distributed)
See the histogram in Appendix A, and descriptive statistics in
Appendix B. A scatter plot is in Appendix C.
Education Level
Thirteen percent of the subjects have no high school degree
while 44% have high school degree. Forty three percent have a
college or college graduate degree. See the bar chart in
Appendix D.
Descriptive Statistics Interpretation
Interpretation
Body Weight
One hundred subjects were randomly selected. Their body
weight was observed between 99 and 234 pounds. Their average
weight was 149 pounds, with a variation of plus or minus 30
pounds. One half or more were above 149 pounds. There is 95%
confidence that the population body weight average is between
144 and 155 pounds.
Age
The data was significantly skewed. One hundred subjects were
randomly selected. Their ages were between 18 and 74 years,
with a variation of plus or minus 10 years. One half or more
5. Instructor’s Name
Descriptive Statistics
Determine the appropriate descriptive statistics.
Note: If the data was normally distributed, use the mean and
standard deviation. If the data was skewed significantly, use the
median and interquartile range.
Numeric Variable Name1
Distribution: State if not normally distributed
Central Tendency:
Dispersion:
Number:
Min/Max:
Confidence Interval: (if distribution is normal)
Numeric Variable Name2 (if applicable)
Distribution: State if not normally distributed
Central Tendency:
Dispersion:
Number:
Min/Max:
Confidence Interval: (if distribution is normal)
Attribute Variable Name (if applicable)
Create a bar chart. Describe the proportions.
Descriptive Statistics Interpretation
Numeric Variable Name1
6. Describe the variable in laymen terms.
Numeric Variable Name2 (if applicable)
Describe the variable in laymen terms.
Appendix A
Raw data used in the analysis
Fit data to one page.
Appendix B
Charts and Tables
This part of the paper will include items that are then cited in
the body of the paper. Usually, large items are placed here not
to distract from reading the paper.
Appendix C
Descriptive Statistics
This part of the paper will include descriptive statistics.