You could pick as many as you like. Ideally you would use all the leaves on the tree, but that would be rather a large number to measure, and your parents might not be very happy if you stripped the tree bare!
So let's try 100 leaves.
How to get a random sample?
Here is one way you could get a random sample:
Try taking all the leaves on one branch of the tree. After you've discarded any that are broken, then see how many there are. If there are less than 100, then get the leaves from another branch until you have more than 100. Then write a different number (starting with 1) on each leaf with a marking pen.
Write the same numbers on small pieces of paper.
Fold the pieces of paper.
Put them into a hat and mix them up.
Draw 100 pieces of paper (without looking) from the hat. The first 100 pieces of paper you draw would give you the numbers of the leaves to use in the experiment.
The next thing you need to decide is how to measure the leaves, and
how accurate your measurements should be:
How to measure?
Keeping your leaves flat, use a ruler to measure the length of each leaf from the pointy part at one end of the leaf to the point where the leaf joins the stalk at the other end. Maybe your leaves bend a bit, but don't follow the main rib of the leaf as this would make measurement too difficult.
Just measure in a straight line as shown in the following diagram:
leaf
How accurate?
You should measure the length of each leaf to the nearest millimeter.
Now you're ready to begin.
Measure the length of each leaf to the nearest millimeter and record you results in a table, as follows:
