the department of energy websi
the department of energy website contains information aboutmonthly wholesale and retail prices for natural gas in each state.go to www.eia.doe.gov/naturalgas/data.cfm and then click on thelink monthly wholesale and retail prices. Under area, choose astate of interest to you, make sure the period Is monthly, and thenunder residential price click on view history. A window will openwith a time plot covering approximately a 25-year period, alongwith a table of the monthly residential prices for each year.
(a) If you have access to statistical software, you should usethe downland data (xls file) link to save the data as an excel(.xsl) file on your computer. Then enter the data into yoursoftware package and reproduce the time-series plot using thegraphic capabilities of your software package. Be sure you use anappropriate title and axis labels. If you do not have access to theappropriate software, provide a rough sketch of the time plot thatis given on the website.
(b) Is there a regular pattern of seasonal variation thatrepeats each year? Describe it. Are the prices increasing overtime?
Answer:
Answer(a): Plot of time series is plotted above. The state ofCalifornia was selected for analysis.
| month | price.seasonality.index |
| January | 99.97584 |
| February | 98.91215 |
| March | 96.11076 |
| April | 95.40866 |
| May | 100.8078 |
| June | 104.0972 |
| July | 104.8449 |
| August | 103.7426 |
| September | 101.9066 |
| October | 101.9417 |
| November | 95.14643 |
| December | 97.10529 |
Answer(b): Seasonality: from the seasonal indexwe can see that there is no any strong evidence of seasonality butthere are slightly higher prices in the moth of June, July andAugust.
Trend: from the trend graph given below it canbe seen that there is increasing trend in the price over thetime.
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