Lab Report on "How Many Drops?"

INTRODUCTION

In the "How Many Drops?" experiment, we are collecting data on the number of drops a coin can hold before it overflows. We then set up an experiment to find the number of drops a penny can hold on its head and tail. We used six pennies to find the number of water drops the head could hold and six more pennies to find the number of water drops the tails can hold. Then we compared the data to find which side is capable of holding more water.

DATA COLLECTION METHOD

In our Lab 2 experiment, we were trying to find out the number of water drops a penny can hold before the water overflows. The "experimental units" in the experiment are pennies. The explanatory variable in this experiment is the side that the water is being dropped on. Therefore, the levels are heads or tails. The response variable is the number of drops the penny can hold before it overflows. When counting the numbers of water drops, we charted the number of drops before the water overflowed. When I started the experiment, I didn't expect a penny to hold that much water. I predicted that a penny would hold about 15 drops of water. I also expected the tail to hold more water because it appeared to me that the tail designs took up less space than the head.

When selecting the pennies, I randomly grabbed 12 pennies. Then to separate them into two groups, I numbered the pennies from 1-12. I thought using the random digit table will take too long so I wrote each number on equally sized individual pieces of paper. I mixed the numbers up and picked 6 pieces of paper. The numbers were 1, 2, 5, 8 and 9. The coins with the corresponding numbers would have heads up and the other coins would be tails up.

Experimental design

I. We first need to gather our materials: eye dropper, water and 12 pennies

2. Then number the coins from 1-12 and write these numbers on small individual piece of paper.

3. Mix them up and pick 6 of these papers. The numbers you draw are the coins with heads showing and the other coins will have the tail showing.

4. The next step is to find the number of drops of water the heads or tails of the coin could hold. Make sure the same person does the dropping each time.

5. Fill the dropper with water and hold the dropper straight up over the center of the coin. Chart the number of drops the coin could hold and which side is showing on the coin.

6. Repeat step 5 for each coin.

There are several lurking variables in this experiment. One lurking variable that could exist in this experiment is the size of the drops that fall for the dropper. To minimize this, we had the same person doing the dropping for each coin. Another lurking variable in the experiment occurs when we select which coin goes to which group. To try to eliminate any bias in selecting the coin, we randomized it by writing numbers on equal sized paper and randomly chose six of them. The way I held the dropper could also cause misleading data because the way I held the dropper could cause a variation in the size of the water drops. Therefore, I made sure that I held the dropper straight up when I was doing the dropping.

RESULTS

 Heads Up Tails up Penny Number Number of drops Penny Number Number of drops 1 33 3 30 2 27 4 34 5 24 7 33 6 29 10 25 8 27 11 32 9 27 12 31

Figure 1

 Mean Median Drops on Heads 27.83 27.00 Drops on Tails 30.83 31.50

Figure 2

Figure 3

DISCUSSION