IB Genetic Lab

---

Observations

Table1: Thirty-three females with age that range from 5 to 50 years, and each female’s arm span and height, collected by surveying them in person

Analysis

Figure 1: The length of arm-span and height of females from age 5 to 50 in centimeters

collected from personal surveys

The mean for the length of arm-span and height can be calculated using the following equation:

                 

Let A represent the average length of arm-span of females.

Let B represent the average height.

A = 160.0cm                                        

B = 159.0cm

The standard deviation can be calculated using the following equation:

                                 

Let A represent the average length of arm-span of females.

Let B represent the average height.

sA = 17.6                                        

sB = 16.9

A Student’s t-test can also be used using the following equation:

            

           t = 6.9 x 10-2

 

Table 2. comparison of length of arm-span and height of females from age 5 to 50.

Figure 2: The mean length of arm-span and height of females from age 5 to 50 in centimeters

collected from personal surveys

Conclusion

When comparing the two means, 160.0cm and 159.0cm, as shown in Table 2 and Figure 2, there are no significant difference between the two means as hypothesized. This is supported by the fact that the t-value, which is 6.9 x 10-2, is smaller than the critical value at p=0.05, which is 2.308, as displayed in Table 1. Table 2 and Figure 2 that display the mean length of arm span and height, which are 160.0cm, and 159.0cm, respectively, indicate that the two values only differ by 1.0cm, which clearly demonstrate that there is no significant difference between the two data. Also in Figure 2, the two bars, which represent the mean length of arm span and height of females from age 5 to 50, barely depict any significant differences. This supports the hypothesis, which was that the length of arm span will be similar. The recorded values of arms span and height in Table 1 also support the hypothesis, for example, 170.0cm measured for the arm-length, which is very close to the value of 170.1cm recorded for height. Furthermore, in Figure 1, a straight, diagonal line of best fit is plotted with the points that represent the values for length of arm span and height, which indicate that the length of arm span and height are proportional to each other, ultimately supporting the hypothesis. However, several values of the length of arm span and height in Table 1 and Figure 1 that show bigger differences than most values suggest that some errors occurred during the experiment.

Evaluation

        Once source of error in the experiment was due to the sample size in the investigation. Only 32 females were surveyed for the investigation, hence, it produced a small sample size for the experiment. The problem is that when investigating heritable factors, surveying small number of people can lead to differing conclusions because heritable factors, which were the length of arm span and height in this investigation, differs from person to person. Due this variety, it is risky to rely on such small sample size. For example, there are females whose length of arm span and height differ greatly, and some whose length of arm span and height are very similar, or in some cases, the same. Thus, to prove the hypothesis, surveying more females would be more reliable. However the 32 females that were surveyed in this experiment produced sufficient amount of data to come to a conclusion and prove the hypothesis, which was that the length of arm span will be similar to the height of females, and that there is a clear association between the two factors. This error can be improved in the future by increasing the sample size. This could be done by surveying more females to ensure that a solid conclusion can be drawn from numerous amounts of recorded values, and to increase the reliability of the experiment.

        Another source of error occurred when measuring the height of females. The height was measured using a measuring tape from the bottom of the individual’s feet to the top of her head. The problem occurred when reading the value on the measuring tape. Although one of the controlled variable was to ensure that all people who were surveyed removed their shoes so that no extra height could be recorded, there was no method of controlling the indicator for the top of an individual’s head. The measuring tape was used to measure the height along the individual’s side rather than the front or the back, so the measuring tape could not be manipulated to bend towards individual’s head, and this left much space between the top of the female’s head and the measuring tape, which firmly stretched along the side of the individual. This also allowed the surveyor to estimate the point on the measuring tape that would have been parallel to the top of the female’s head, hence leading to collecting inaccurate data. However, a conclusion was still drawn and supported the hypothesis, which was that the length of arm span will be similar to the height. This error can be improved in the future by using a thin flat book or a ruler to indicate and read the measuring tape more accurately, and to ensure that the number on the measuring tape is parallel to the top of the head, and also ensuring that no extra height has been added with hair. This will improve the collection of accurate data in the investigation.

---

Student's t-Test: Results

The results of an unpaired t-test performed at 21:14 on 3-JUN-2008

t= 0.695E-01
sdev= 17.3
degrees of freedom = 62

The probability of this result, assuming the null hypothesis, is 0.945

Group A: Number of items= 32
110. 126. 129. 132. 134. 145. 148. 154. 155. 155. 155. 157. 162. 162. 164. 164. 166. 168. 168. 168. 169. 169. 169. 170. 170. 170. 171. 172. 180. 181. 182. 184.

Mean = 160.
95% confidence interval for Mean: 153.5 thru 165.7
Standard Deviation = 17.6
Hi = 184. Low = 110.
Median = 165.
Average Absolute Deviation from Median = 12.7

Group B: Number of items= 32
112. 127. 129. 133. 134. 144. 153. 153. 154. 154. 155. 157. 160. 160. 161. 163. 163. 167. 167. 168. 168. 169. 169. 170. 170. 170. 171. 173. 180. 180. 181. 182.

Mean = 159.
95% confidence interval for Mean: 153.2 thru 165.4
Standard Deviation = 16.9
Hi = 182. Low = 112.
Median = 163.
Average Absolute Deviation from Median = 12.4

---