## Thumb Measurement

Donald Galen

Introduction

This exercise deals with both the metric system and the statistical analysis of data taken from the human hand. You will learn how to make bar graphs from the statistics you collect. The many people in our world with two recessive genes for hitchhiker's thumb are able to bend the distal joint of that digit. They can bend their thumbs at an angle of 45 degrees or more. This is called hyperextension of the thumb. People who carry either one allele or two alleles for a thumb that is straight, or close to being straight, are said to express the dominant gene.

1. Materials

1. 1- thumb
2. 1- metric ruler, mm and cm
3. 2- graphs

2. Procedure

1. By using the picture below, measure your thumb in millimeters from joint 2 to the tip of your finger. Do not include the measurement of your fingernail.

2. Record whether or not you have a hitchhiker's thumb on the chart on the second page of this exercise.

3. Record your measurement in millimeters in column A if you have a hitchhiker's thumb and in column B if you have a straight thumb.

4. Record the measurements of your classmates' thumbs on the remaining part of this chart and determine average or mean for A and an average or mean for B.

5. Copy the graph picture provided to your graph paper, graph the length of the thumb in mm on the Y axis, and record your class data using a bar graph. Do only two columns in your graph, column A and column B, hitchhiker's thumb and non-hitchhiker's thumb.

6. Add the hitchhiker's thumb data from all of the classes (chart 2) and find the average. Do the same with the straight thumb data.

7. Make a second bar graph with your two averages from #6 above.

3. Picture of a Thumb

(You should use this picture to determine what to measure)

4. Picture of a Hitchhiking Thumb

5. CHART AND GRAPH
1. Do you have hitchhiker's thumb? Circle your answer: YES NO
2. If you have a hitchhiker's thumb, put your results in column A, and if not, put your results in column B. Add your fellow classmates to the remaining part of the chart.

6. CHARTS FOR ALL OTHER BIOLOGY CLASSES:
1. Record the data of other biology classes in the chart below.
2. Put the hitchhiker's thumb trait on the left side of column A and the non hitchhiker's thumb trait on the right side of column A.
3. For each additional biology class, record the data in columns B, C, D, and E just like you did in number 2 above.

KEY TO THE CAHRT BELOW:

• Column A = class 1
• Column B = class 2
• Column C = class 3
• etc.

7. Analysis Of Data

For a simple exercise (without formal statistical analysis), a variation may be considered significant if you have at least a 20 percentage point or higher variation for hitchhiker's thumb. To calculate this, you may use the following formula:

• ( 1- B/A) x 100 = % difference in mm
• A = mm average x no. of people (hitchhiker's thumb)
• B = mm average x no. of people (no hitchhiker's thumb)

For those who would like to consider statistically significant differences use a t test which considers sample size. This will allow you to calculate whether there is a significant difference between your samples.

8. Using the Formula

1. Calculate the % difference for your class (graph) and record your answer here.

2. Calculate the % difference from the additional biology classes (2nd graph) and record your answer here.

3. Did the additional biology classes have a significant variation for having a longer hitchhiker's thumb? (Circle: YES NO.) If yes, how much?

4. Did having more people randomly involved make a difference in your results? (Circle YES NO.) How did you know this?

5. Summarize what you have learned in this exercise about percent differences in the average or mean of data. Write at least one paragraph.

9. Further Studies (Using the data available)

1. Determine the mean, medium, mode, range, and standard deviation.

2. Demonstrate the Hardy-Weinberg Equilibrium.

3. Randomly select 100 students on your campus and compare this data with the data taken in this exercise.

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