Early or Late? What's the Range, Median and Mean? Will our gardens be emerging and blooming late or early this year? How can you make an accurate prediction? First you will need some good data – the more years worth the better. Looking carefully at data helps us to make better predictions. Beam Down to Pequot Lakes, MN! These students have really been dedicated Garden Study scientists. Their garden site is located near 46.7 degrees North latitude where winter cold can really send a chill down your spin. They have planted tulips for 8 years in a row. Let’s explore how we can analyze their data... ...but first some mathematical terms: Range: The difference between the earliest and latest dates in a set of data. Median: The median is the 50th percentile. The date in an ordered set of data such that half of the dates are earlier and half of the dates are later. Half the values are larger than the median, and half are lower. If there are an even number of values, the median is defined as the average of the two middle values. Mean: The mean is the average of all the values. It's 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. Try This! Analyze This Data Here are emerging dates for tulips in Pequot Lakes, MN: 3/24/97, 2/23/98, 4/01/99, 3/25/00, 4/05/01, 4/22/02, and 4/18/03. Let's take a close look at the data: Make a stem-and-leaf plot, arranging the data in order from earliest to latest date of sighting. Count the number of days between the earliest and latest arrival dates. This difference is the range of emerging dates for Anchorage. Next figure the median emerging date. Your data are already in order, so you can see on which date half of the records are earlier and half of the records are later. (Because there is an even number of records, you'll need to find the average of the two middle values.) Finally, calculate the mean emerging date. (The mean is the concept most people think of as the "average.") When using calendar dates, this can be tricky. Before reading the example on the worksheet, challenge yourself to think this through! Compare YOUR Solution to This: Link to our Student Worksheet Keep Track of Your Own School's Tulip Records Look it up: Your Own Tulip Records Check out your own school records. Use the Student Worksheet for predicting when YOUR school's tulips will emerge. Will it be earlier, or later than the mean dates? Copyright 2003-4 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form