posted by .

A class is to perform an experiment to study the effects of various plant foods on a type of indoor plant.The teacher provides three similar plants,a water supply,and three different packets of plant food.Explain how you might conduct a controlled experiment.

  • science -

    Wouldn't you use only one type of food on one plant consistently?


  • science -

    The plant food is the independent variable, probably the amount of growth during a specified period is the dependent variable, and the amount of water is one extraneous variable. Another extraneous variable would be the amount of sunlight each plant gets. As a better control, it would be good to have a fourth plant that gets no plant food.

    A review of the experimental method might be helpful.

    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.

    Extraneous variables — other than the independent variable — potentially can affect the dependent variable, so they must be controlled. If possible, you try to keep them constant between the experimental and control group.

    The experimental group receives the independent variable.

    The control group is similar to experimental, except it does not receive the independent variable. Extraneous variables are balanced between experimental and control groups.

    Types of experiments

    1. Single blind gives the control group a placebo — a substance that is inert, it has no physical effect. Subjects don't know if they are in experimental or control group to reduce placebo effect, a change in behavior solely due to believing that you are getting the independent variable.

    2. Double blind keeps both subjects and experimenter ignorant of group setup. Distribution of the independent variable and placebo are controlled by third party. This controls for experimenter bias and self-fulfilling prophecy, which means that experimenters with particular expectations are likely to consciously or unconsciously to bias the experiment and influence it to conform to their expectations.

    As an example, suppose you want to find out if fluorides reduce dental cavities. You would find two groups, trying to control the extraneous variables. Extraneous variables are found by surveying previous research in the area. In this case, you would match the groups in terms of previous history of cavities, diet and dental hygiene habits including how and how often they brush their teeth.

    The experimental group would get toothpaste with the independent variable, the fluoride, while the control group would not have the fluoride in their toothpaste. The toothpaste without the fluoride would be the placebo.

    The dependent variable would be the number of cavities after participating in the experiment for a time. The dependent variable indicates the results, but it is not the results. At the end of the experiment, both groups could have no change in cavities or one of the groups could have a greater reduction in cavities. (Of course, if the fluoride increased cavities, you wouldn't want to use it.) All of these varied results would be indicated in terms of the dependent variable.

    If only the subjects do not know who is getting the fluoride, it is a single blind experiment. If both the subjects and experimenter do not know, it is a double blind.

    I hope this helps a little more. Thanks for asking.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. check/bio!!!!

    okay the question is as follows: Three plants are placed in 3 different terrariums in 3 different light conditions. Plant A is placed in blue light, plant B in green light, and plant C in yellow light. In which case will there be an …
  2. Science

    What could happen if a plant’s phloem does not work correctly?
  3. science help plzzz

    Multiple Choice 1. Which of the following images shows a living organism interacting with a biotic factor in its environment?
  4. Science

    A plant deprives of light dies. Which of the following best explains why this happens?
  5. biology

    jordan is doing a science fair project on the effect of music on the growth of tomatoes. he has two tomato plants, plant A and B, that he grows in a window and gives the same amount of water. plant A is exposed to classical music using …
  6. biology help please :)

    Olga's teacher asked her to design an experiment using freshwater plants, fish bowls, tap water, and salt. After determining an approach, Olga placed a plant in each of three fish bowls. Then, she filled one bowl with fresh water, …
  7. science help

    A student did an experiment with two identical plants, Plant 1 and Plant 2. About 10 mL fertilizer was added to Plant 1. About 200 mL of water was added to each plant every day. The height of the plants was recorded over a period of …
  8. science help check

    Which of these is an example of an experiment?
  9. Science

    Bob created an experiment to test what plants need to survive. He believes plants only need water to live. In order to test his hypothesis, Bob planted two of the same types of plant. Only one received water and sunlight. While the …
  10. Science

    Jordan is doing a science fair project on the effects of music and growth of tomatoes.he has two tomato plants, plant A and plant B that he grows in a window and gives the same amount of water. Plant A is exposed to classical music …

More Similar Questions