The quadrat method is frequently used to count plant populations over a large region.

For this method:

• Drop some sunflower seeds on a checkerboard.
• Choose 4 squares at random using the TI-82 program SELECT.
• Count the sunflower seeds in those 4 squares.
• Multiply your answer by 16.

How can this be used to estimate the total population?

To take an example, say you count 15 sunflower seeds in the four squares.

What does that tell you?

• The total number of seeds on 4 squares is 15.
• The total number of seeds on 4 squares is about 4/64 = 1/16 of the total number of seeds.
• Thus the total number of seeds is about 15 X 16 = 240.

If you start with a map of a region:

• Place a clear rectangular grid over the map.
• Number the rectangles in the grid - 1,2,...,N.
• Decide how many rectangles you plan to use. Call this number C.
• Choose C rectangles at random using the TI-82 program SELECT.
• Count the population in the selected rectangles.
• Multiply this count by the total number of rectangle and divide by the number of chosen rectangles.