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**Data**: etmgeg_380.zip ### Instructions

## Exercise 3974. Points 3, theme: Directions |
Open exercise |

The web site of Dutch climate contains public climatological data. The observation data for Maastricht is added to this exercise. Find from it the wind speed and direction data for years 1906-1912 and 2006-2012.

- What is the wind speed-weighted mean direction and the 95% confidence limits of the mean during these periods?
- Is the difference in mean values statistically significant?
- Has the total air flow origin turned to the south or to the north during this 100 years period?

- Download the attached file.
- Mark comma as the column separator while opening the file in Excel.
- Select the first interval in the columns DDVEC and FHVEC.
- Open directions in the online calculator. Select
*Cases have weights*. - Paste the copied values to the input box in the calculator.
- Launch calculation and save the results.
- Repeat the calculation using data from the second interval.
- Compare the mean values for intervals. Is a mean of one sample within the confidence limits of the other mean value?

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