Calcluating the Mean
Tulip Emerging Dates
People always
wonder, when will our tulips emerge? You can use historic event records
collected in a single place to calculate the "mean" date.
The mean
date is the the most common measure of center. To determine the mean,
find the sum of the values in the set, then divide by the number of values.
To calculate
the mean using calendar dates, it helps to rank them, or put the dates
in order, and to assign each date a number. The example on the chart below
uses the emerging dates for Pequot Lakes, MN. Their tulips emerged on
2/23/98, 3/24/97, 3/25/00, 4/01/99, 4/05/01, 4/18/03, and 4/22/02.
- Put the
dates of emerging tulips in order by month and day. (This has been done
for you.)
- Enter
dates on the chart calendar. (Earliest date goes on the first line,
then count down days down til you reach the next date.) Use the order
number beside each date for its value.
- Add all
the values for all the dates
- Then divide
by the number of emerge dates. The result is the order number. Find
the order number on the chart and calculate the date. This is the mean
arrival date.
- The chart
has space for you to calculate the mean emerging date for your home
town.
Order
(value) |
Date
of Emerging Tulips
in Pequot Lakes, MN |
Date
of Emerging Tulips
in My Home Town |
1
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2/23/98 |
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2
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3
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4
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5
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6
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7
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8
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9
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10
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11
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12
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13
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14
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15
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16
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17
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18
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19
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20
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21
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22
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23
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24
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25
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26
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27
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28
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29
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30
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3/24/97
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31
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3/25/00 |
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32
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33
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34
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35
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36
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37
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4/01/01 |
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38
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39
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40
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41
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4/05/01 |
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42
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43
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44
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45
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46
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47
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48
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49
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50 |
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51 |
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52 |
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53 |
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54 |
4/18/01 |
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55 |
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56 |
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57 |
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58 |
4/22/01 |
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