Transcript Regional Gas Price Change Over Time

Regional Gasoline Price Change
Kristal Chin, Heather Coleman, Yuyuan Liu, Karen
McNeany, David Parker, Laura Pomella, Yongyang Yu
Question
• Are gasoline prices different across the country ?
• Ho(1): 1993–2005 prices are regionally equivalent
• Ha (1): West Coast prices have been higher than
in other regions of the U.S.
• Ho(2): 1993–2005 prices change at the same rate
• Ha (2): West Coast prices have increased more
quickly than in other regions of the U.S.
Data Set
• U.S. Department of Energy (EIA)
• U.S. Regular Weekly Retail gas prices from
April 1993 – November 2005
• Country divided
into eight regions
for analyses
Data Set
Regional Gasoline Prices from April 1993 to November 2005
350
Gasoline prices (cents per gallon)
East Coast
300
New England
Central Atlantic
Lower Atlantic
250
Midwest
Gulf Coast
Rocky Mountain
West Coast
200
150
100
50
1
51
101
151
201
251
301
351
401
Time index (weeks)
451
501
551
601
651
Data Set
Gasoline Price Histograms
200
Series: WESTCOAST
Sample 1 660
Observations 655
80
60
40
150
Mean
Median
Maximum
100 Minimum
Std. Dev.
Skewness
Kurtosis
50
Jarque-Bera
Probability
20
148.0446
137.7000
297.4000
102.5000
36.08569
1.619988
5.759430
494.3039
0.000000
Series: AVGWOWEST
Sample 1 659
Observations 659
200
Series: WESTCOAST
Sample 1 660
Observations 655
150
Mean
148.0446
Median
137.7000
Maximum
297.4000
100
Minimum
102.5000
Std. Dev.
36.08569
Skewness
1.619988
Kurtosis
5.759430
50
Mean
Median
Maximum
Minimum
Std. Dev.
Skewness
Kurtosis
135.1150
123.5000
310.6714
89.68571
35.66161
1.718967
6.556075
Jarque-Bera
Probability
671.7699
0.000000
Serie
Samp
Obse
Mean
Medi
Maxi
Minim
Std. D
Skew
Kurto
0
200 220 240 260 280 300
Jarque-Bera
80 100 120 140 160 180 200 220
240 260 280 494.3039
300 320
0
100 120 140 160 180 200 220 240 260 280 300
West Coast
Probability
0.000000
0
80 100 120 140 160 180 200 220 240 260 280 300 320
Average of Other Regions
Jarq
Prob
Statistics
1. F - tests determine whether variances of prices on the
West Coast and each other region are equivalent
• The p - value for each F - test was > 0.05
2. Two sample t - tests determine whether West Coast
prices are equivalent to each of the other regions
• The p - value for each t - test was <<< 0.05
3. Dummy variable ANOVA tests (1) including West
Coast and (2) using C instead to represent it
• Coefficients are significantly different, and
therefore the West Coast has higher prices
Data Set
Linear Regression of Gasoline Price Change
Gasoline prices (cents per gallon)
Regional Gasoline Prices from Apr. 2003 to Nov. 2005
350
West Coast
Other Regions
300
250
200
West :
150
y = 0.1473x + 99.216
R2 = 0.6008
100
Other (avg) :
y = 0.1459x + 86.966
2
R = 0.6067
50
0
100
200
300
400
Time index (weeks)
500
600
Statistics
1.2 and Whisker Plot compares the regional
Box
Series1
1
rates of gasoline price increase
0.8
0.6Gulf
Rocky
Mountains
Coast
0.4
West
Coast
New
England
0.2
0
0.135
0.1375
0.14
0.1425
0.145
0.1475
0.15
0.1525
0.155
0.1575
Cents/Gallon
Week Index
Mean
Price
Conclusions
1. Every region of the U.S. has statistically
significantly lower gasoline prices than the
West Coast region
2. The prices on the west coast increase more
quickly than the average of all other
regions, but not statistically significantly