Biological Science - How to Experiment

Science

Science deals only with the real world, carefully collecting and organizing information to propose an explanation that can be tested through predictions about a prediction in the world.

     Examples include Biology, Chemistry, and Physics, but not Astrology.


For the scientific method, you need a problem or a question to create a hypothesis for. The scientific method can be simplified into five steps:

  1. Observe (figure out what problem to solve or question to answer

  2. Hypothesize (make an idea about the question/problem you can test)

  3. Experiment (test the question/problem)

  4. Analyze (collect data from the test)

  5. Conclude (interpret the data in relation to the hypothesis)


There is a difference between a hypothesis and a theory.

  • A hypothesis has not been tested much or at all.

  • A theory is a hypothesis that has been tested more extensively and is backed by evidence.


Experiments have an independent and dependent variable:

  • An independent variable (also known as the “manipulated” variable) is what changes in an experiment. In a plant experiment, it might be the kinds of fertilizer the plants receive.

  • A dependent variable is what is measured during the experiment. In a plant experiment, it might be how high the plants grow.


Experiments can also be controlled. This means that part of the experiment involves an unaffected or “normal” version of the thing being tested. This is so the object affected by the independent variable can be compared to the control.

Statistics

Stats validate claims. With the results of your experiment, you have to see how likely your outcome was to support your hypothesis.

The normal curve or bell curve is a typical way to show statistical information. It has the mean in the middle, with three standard deviations on either side.

    There is also the 68/95/99 rule about these standard deviations: 68% of the data is within 1 standard deviation, 95% is within 2 standard deviations, and 99% is within 3 standard deviations.

Alpha is the significance threshold to compare the results to. It’s usually .05.

A t-test is a statistical test that compares means between two groups.

    T = (mean 1 - mean 2) 1 standard deviation

A Critical Value is the “rejection region” where reaching this value leads to a rejection of the null hypothesis, or proof of a relationship between variables.