2. Hypotheses
1. As the salt concentration increases, the amount of E.coli growth over 24 hours decreases.
2. As the glucose concentration increases, the amount of E.coli growth over 24 hours also increases. 3. The optimal pH for E.coli growth is 7.0.
4. The E.coli is not tolerant of any of the antibiotics.
5. The optimal temperature for E.coli growth is 37๐C.
3. Independent Variables
1. In the salt test, the concentration of salt was altered.
2. In the glucose test, the concentration of glucose was changed.
3. In the pH test, the pH was altered.
4. In the antibiotic test, the type of antibiotic was changed.
5. In the temperature test, the temperature was the independent variable.
4. Dependent Variable
For the salt, glucose, pH and antibiotic tests, the measured variable was the radius around the test discs that was clear of E.coli growth after 24 hours. For the temperature test, the measurable variable was the number of colonies that grew in a 24 hour period.