Passengers (thousands) 150000 145000 140000 135000 130000 125000 120000 115000 110000 Time Series plot of quarterly light rail usage (first quarter 2015 through third quarter 2024) wwww 0 8 12 16 20 Time (Quarters) 24 28 32 36 40 40 Year Quarter t y(t) 2015 1 1 110569 2 2 113433 3 3 118183 4 4 114932 2016 1 5 112337 2 6 117224 3 7 118863 4 8 116554 2017 1 9 116287 2 10 124077 3 11 126540 4 12 123559 2018 1 13 122607.4 2 14 129549.7 3 15 128105.9 4 16 126818.9 2019 1 17 123020.3 2 18 130158.9 3 19 133584.3 4 20 132147.9 2020 1 21 126932.4 2 22 123051.92] 3 23 134041.56 4 24 135031.20 2021 1 25 130020.840 2 26 128010.480 3 27 138000.12 4 28 139989.76 2022 1 29 140979.40! 2 30 135969.04 3 31 130958.68! 4 32 142948.32! 2023 1 33 144321.12! 2 34 139782.059 3 35 135372.74 4 36 147611.86 2024 123 37 149334.83 38 145124.004 39 141022.359
Figure 1 below displays the quarterly number of U.S. passengers (in thousands) using light rail as a mode of transportation. The series begins in the first quarter of 2015 and ends with the third quarter of 2024.
We can see a regularity to the series: the first quarter’s ridership tends to be lowest; then there is a progressive rise in ridership going into the second and third quarters, followed by a decline in the fourth quarter. Superimposed on the series are the moving-average
Notice that the seasonal pattern in the time series is not present in the moving averages. The moving averages are a smoothed-out version of the original time series, reflecting only the general trend in the series, which is upward.
Data Analysis Questions:
1. Calculate the centered moving average (CMA) that will be centered on t = 3.
This value can be seen in the spreadsheet below. Show the centered moving averages plotted on the passenger series y(t) and compare and interpret the trend of two series. Do not forget to label x and y axes and adjust the values on the plot using Figure 1.
Show your plot space provided below:
Now you have an appropriate baseline estimate for the level of the process historically, so you can compute the seasonal component. This seasonal ratio says that we can isolate the seasonal component by dividing the data by the level of series as estimated by the trend component.
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