The Breaking Force of Hair Lab

Data Processing and Presentation

Table #1: Mean and Standard Deviation of Blow Dried Hair and Non-Blow Dried Hair Data

Type of Hair

Mean (N � 0.01 N)

Standard Deviation (N)

Non-Blow Dried Hair Force

2.08

� 0.68

Blow Dried Hair Force

1.70

 0.83

Note: Microsoft Excel 2007 was used to calculate mean and standard deviation.

Note: Error Bars represent standard deviation. Units and uncertainties are not applicable for the independent variable (type of hair).

Degrees of Freedom

Sum of Samples of Each of the Two Groups – 2

= 50 + 50 – 2

= 98

An approximate value of 100 was used as the degrees of freedom for use in the t-table.

Probability due to chance

Given the t value for the non-blow dried hair compared to the blow dried hair is 1.97, the t-table can be used to find the probability that the difference between the two groups is due to chance. The t value of 1.99 was used an approximate t value, since a 1.97 value in the 100 degrees of freedom rows does not exist. Therefore, the probability that the difference between the two groups is due to chance is 0.05 (5%).

Range

Non-Blow Dried Hair Force

Blow Dried Hair Force

Range = Largest value – Smallest Value

= 3.47 – 0.85

= 2.62

Range = Largest value – Smallest Value

= 3.88 – 0.03

= 2.85

Conclusion

The average hair breaking force of non-blow dried hair is 2.08 N 0.01 N, with a standard deviation of 0.68. The average hair breaking force of blow dried hair is 1.70 N 0.01 N, with a standard deviation of 0.83. The average of the hair breaking force of non-blow dried hair is greater than the hair breaking force of blow dried hair. This means that blow dried hair is weaker than non-blow dried hair. Since the standard deviation for the non-blow dried hair is less than the standard deviation of the blow dried hair, we are more confident of the accuracy of the non-blow dried hair data, and the blow dried hair data is more variable.

References:

“The Structure of Your Hair.” Salon Web. 1996. <http://www.salonweb.com/chem>