Lab Exercise 1 - Scientific Inquiry in Biology
In this lab, we will be using a case study involving Lays® potato chips.
Background:
Fats are chemically stored as triglycerides in the adipose tissue of humans. The structure of triglycerides consists of a glycerol backbone attached to three fatty acids (see the biological molecules chapter of your textbook). Olestra® is synthesized from sucrose and can bond with six, seven, or eight fatty acids.
The resulting molecule is structurally too large and irregular to move through the intestinal wall of the small intestine. Since humans have no evolutionary experience with this molecule, no digestive enzymes are able to break apart this molecule into its simpler components.
Olestra® has the same taste as fat, but it passes through the gastrointestinal tract undigested without contributing calories or nutritive value to the diet.
Lays® potato chips bought the patent on this synthetic fat, originally developed by Johnson and Johnson. In the late 1990s, WOW potato chips were commercially released for sale. Shortly thereafter, consumers began complaining about diarrhea, gas, cramps, bloating and general gastrointestinal distress.
Observation:
Olestra® potato chips contain a synthetic fat, not digestible by humans. Synthetic fats sometimes cause gastrointestinal (GI) distress in humans. In certain cases, intestinal distress results in cramps in humans.
Hypothesis:
Olestra® is the cause of intestinal cramps. This hypothesis is easily tested because if Olestra® is the cause of the cramps then more people who eat them will get cramps when compared with people who eat regular chips.
Assignment Part 1: Establishing the Experiment
- Write a brief description of how you would perform this experiment.
- In your description, be sure to address the following:
- What is the control group?
- What is the experimental group?
- What is the independent variable?
- What is the dependent variable?
- What are some possible controlled variables?Part 2: Data Analysis
Here are some results from a similar experiment to the one you designed, which compared the percent of people who suffer gastrointestinal (GI) distress after eating Olestra® chips with the percent of people who suffer gastrointestinal (GI) distress after eating regular potato chips.
The results from the preliminary experiment set up by the company are as follows:
Treatment
|
Treatment Number
|
Total Number of People
|
Number of People with GI Distress
|
Regular Chips |
1 |
100 |
6 |
Olestra Chips |
1 |
100 |
14 |
Table 1.1
Sampling Error:
If researchers had only used a few people, or only a single data set, in their experiment, they may have the problem of sampling error. For example, if they had only surveyed 10 people, 5 in each group, the likelihood of incorrect results is much higher than with a larger number of people and multiple data sets.
Data Analysis (Continued):
After their preliminary study, the company conducted more experiments as follows. The mean, or average, for these data is calculated by taking the total number with GI distress divided by the total number sampled. The percent is calculated by multiplying that number by 100. The standard deviation indicates the amount of variation in the data set, the amount above and below the mean, drawn as a line in the shape of an “I”.
Treatment Number
|
Total Number of People
|
Number with GI distress
|
1 |
100 |
8 |
2 |
100 |
10 |
3 |
100 |
25 |
4 |
100 |
5 |
5 |
100 |
13 |
Table 1.2. Treatment: Regular Chips
Treatment Number
|
Total Number of People
|
Number with GI distress
|
1 |
100 |
19 |
2 |
100 |
7 |
3 |
100 |
28 |
4 |
100 |
15 |
5 |
100 |
11 |
Table 1.3. Treatment: Olestra® Chips
Assignment Part 2: Data Analysis
- Table 1 Analysis
- Based on the preliminary data, would you accept or reject your hypothesis? Explain why.
- Sampling Error Analysis
- Describe why it is important to increase your data and number of experiments.
- Table 2 Analysis
- Calculate the average number of people with GI Distress in the Regular Chips Group.
- To calculate average: (Total Number of People with GI Distress)/(Total Number of People).
- Table 3 Analysis
- Calculate the average number of people with GI Distress in the Olestra Chips Group.
- To calculate average: (Total Number of People with GI Distress)/(Total Number of People).
- Final Analysis of Table 2 & 3
- Based on the averages of both groups, would you accept or reject your hypothesis?
- In general, does a small sample size or a large sample size give more accurate data.
- Discuss any other conclusions related to the experiment.