Statdisk Instructions for Chapter 6 Technology Exercise

Windmill at Richland (Question 1)

Gathering the Data

The following example assumes that you were assigned "March". You should replace that with whatever month you were given to work with. Do not work with the current month, make sure the month is completely over before collecting data. You should be collecting data for the last two times your month has completely occurred.

  1. Visit the National Weather Service's archive page at http://www.weather.gov/climate/index.php?wfo=ilx.
  2. Chose the Preliminary Climatology Data (CF6)
  3. Choose the Decatur Airport
  4. Choose Archived Data
  5. Select the latest month and year for the month you were given. In this example, it would be March 2005 since March 2006 isn't over yet.
  6. Click Go.
  7. Record the "AVG SPD" for the Wind from column 10 for each of the days in March 2005. While you're at it, you might as well go ahead and collect the "AVG" for the temperature from column 4 because you'll need it for question 2.
  8. Click the Back button and choose March 2004 and Go
  9. Record the "AVG SPD" for the Wind from column 10 for each of the days in March 2004.

Entering the Data into Statdisk

  1. Click on the 1 at the top of the first column and label the first column as wind
  2. If you happened to gather the temperature data, then label the second column as temp
  3. Enter the data into the appropriate columns

Graphical Summary

Statdisk doesn't provide a graphical summary. You'll need to use Minitab for this. You really should use Minitab for the whole thing so you don't have to retype your numbers.

Descriptive Statistics

You can't find the confidence interval directly from the data like you could with Minitab. You need to do descriptive statistics first, write those numbers down, and then go do the confidence interval.

  1. Choose Data / Descriptive Statistics
  2. Select column 1 (the wind data)
  3. Click Evaluate
  4. Write down the sample size, mean, and st dev. Don't round the values.
  5. If you gathered the temperature data as suggested, then go ahead and repeat this with column 2 (the temperature data)

Confidence Interval

  1. Choose Analysis / Confidence Intervals / Mean-One Sample
  2. Enter the confidence level as a decimal
  3. Enter the sample size, sample mean, and sample st dev that you found from the descriptive statistics screen
  4. Leave the population st dev blank
  5. Click Evaluate

When Statdisk gives the confidence interval, it will look something like 5.62333 < mean < 7.31215. You should write it as 5.62333 mph < μ < 7.31215 mph.

Average Daily Temperature (Question 2)

If you already collected the temperature data for question 1, then you can skip straight to the Graphical Summary section.

Gathering the Data

The following example assumes that you were assigned "September". You should replace that with whatever month you were given to work with.

  1. Visit the National Weather Service's archive page at http://www.weather.gov/climate/index.php?wfo=ilx.
  2. Chose the Preliminary Climatology Data (CF6)
  3. Choose the Decatur Airport
  4. Choose Archived Data
  5. Select the latest month and year for the month you were given. In this example, it would be March 2005 since March 2006 isn't over yet.
  6. Click Go.
  7. Record the "AVG" for the temperature from column 4.

Entering the Data into Statdisk

  1. Label an empty column as temp
  2. Enter the data into the temp column.

Graphical Summary

Statdisk doesn't provide a graphical summary. You'll need to use Minitab for this. You really should use Minitab for the whole thing so you don't have to retype your numbers.

Descriptive Statistics

You can't find the confidence interval directly from the data like you could with Minitab. You need to do descriptive statistics first, write those numbers down, and then go do the confidence interval.

  1. Choose Data / Descriptive Statistics
  2. Select the column where you stored the temperature data.
  3. Click Evaluate
  4. Write down the sample size, mean, and st dev. Don't round the values.

Confidence Interval

  1. Choose Analysis / Confidence Intervals / Mean-One Sample
  2. Enter the confidence level as a decimal
  3. Enter the sample size, sample mean, and sample st dev that you found from the descriptive statistics screen
  4. Leave the population st dev blank
  5. Click Evaluate

When Statdisk gives the confidence interval, it will look something like 74.3824 < mean < 77.6821. You should write it as 74.3824 °F < μ < 77.6821 °F.

Normal Average Temperature

Visit the Weatherbase at http://www.weatherbase.com/. Do a search for "Decatur, IL" and find the average temperature for your month.