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Predicting tropical storms William Gray heads the Tropical Meteorology Project at Colorado State

University. His forecasts before each year鈥檚 hurricane 2008season attract lots of attention. Here are data on the number of named Atlantic tropical storms predicted by Dr. Gray and the actual number of storms for the years 1984 to 2008:

Analyze these data. How accurate are Dr. Gray鈥檚 forecasts? How many tropical storms would you expect in a year when his preseason forecast calls for 16 storms? What is the effect of the disastrous 2005 season on your answers? Follow the four-step process.

Short Answer

Expert verified

DR.G鈥檚 forecasts are not very accurate.

There are 16tropical storms

The effect of the disastrous has a little effect.

Step by step solution

01

Given information

YearForecastActualYearForecastActual
198410121997117
1985111119981014
19868619991412
19878720001214
1988111220011215
198971120021112
1990111420031416
19918820041414
19928620051527
19931182006179
19949720071714
1995121920081516
19961013


02

Concept

Linear regression is commonly used for predictive analysis and modeling.

03

Calculation

To begin, plot the forecast (X) as an explanatory variable and the actual number of storms as the response variable in a scatterplot. Fit a least-squares line to the data if the graph has a linear form. Then plot the residuals. The residualsr2 and s indicate how well the line fits the data and the magnitude of our prediction mistakes. A scatterplot of the data is shown in the diagram below. The scatterplot reveals a positive relationship. In other words, if there are more forecasts, there are more actual storms. The entire pattern is relatively linear (r=0.5478 according to a calculator). On the scatterplot in the Y-direction, there is one outlier.

Using the MINITAB, the regression equation is shown below

The least-square equation is y=1.69+0.915X

Using the MINITAB, the residual plot is shown below:

The slope indicates that the actual forecast increased by 0.915 for each additional forecast. The Y-intercept is the value of Y when X=0; for example, if the forecast is O, the actual storm number will be 1. The residual plot was used. The scatter points around the "residual = 0" line are rather "random," with one extremely large positive residual (point for the year 2005). On the forecast scale, the majority of the prediction mistakes (residuals) are 10 points or less. The standard error of the residuals was calculated to be s=3.9983 This is around the amount of an average regression line prediction error. Since =0.3001, the least-squares model has accounted for 30.01 percent of the variation in the actual number of storms.

Use the equation

Actual storm =1.69+0.915(forecast)

To estimate the number of storms that will occur based on the prediction. However, our projections may not be particularly accurate. It's risky to make predictions with this model. If Dr. Gray's preseason prediction is correct, then

Actual storm

=1.69+0.915(forecast)=1.69+0.915(16)=16.33

Consider the below figure:

The outcome of eliminating the 2005season from the correlation and regression line is seen in the graph above. One extra regression line is added to the graph once the 2005season has ended. Removing this point has no influence on the regression line, as can be shown.

Therefore, DR.G鈥檚 forecasts are not very accurate. There are 16tropical storms. The effect disastrous has a little effect.

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