A group of students are setting up the first experiments, looking at the growth of roots in water containing an added factor. They have decided to grow seeds in both in pure tap-water and in water with a defined amount of vinegar added. As part of their group discussions they are keen to ensure that they all know what are the dependent variables that they are measuring in the experiment.
which two of the following would count as dependent variables in this experiment
1) How many seeds each student is using in the experiment.
2) The type of vinegar used.
3) The intensity of light that the seedlings experience.
4) The concentration of vinegar used.
5) The number of seeds which have germinated.
6) The length of the root.
nces.ed .gov/nceskids/help/user_guide/graph/variables.asp
An independent variable is the potential stimulus or cause, usually directly manipulated by the experimenter, so it could also be called a manipulative variable.
A dependent variable is the response or measure of results.
5 and 6.
In this experiment, the dependent variables are the variables that are being measured and are expected to be influenced by the independent variable, which is the addition of vinegar to the water. The two dependent variables in this experiment are:
5) The number of seeds which have germinated: This variable measures the effect of adding vinegar on seed germination. The students will count and record the number of seeds that have successfully germinated in each condition (pure tap water and water with vinegar added).
6) The length of the root: This variable measures the effect of adding vinegar on root growth. The students will measure and record the length of the roots of the germinated seeds in each condition to determine if there are any differences in root growth between the two conditions.
The other options given are not dependent variables as they do not directly measure the effect of the independent variable (vinegar) on the growth of roots in water. Here's an explanation of what each of the other options represents:
1) How many seeds each student is using in the experiment: This is not a dependent variable. It is a controlled variable that the students could use to ensure consistency across their experiments.
2) The type of vinegar used: This is not a dependent variable. It is an independent variable that the students have decided on as part of their experimental setup.
3) The intensity of light that the seedlings experience: This is not a dependent variable. It could be a controlled variable that the students keep consistent across their experiments, but it is not being measured or expected to be influenced by the addition of vinegar.
4) The concentration of vinegar used: This is not a dependent variable. It is an independent variable that the students have decided on as part of their experimental setup.