Analyzing Data

When we talk about analysing data we usually mean ‘doing statistics’ but it’s always wise to evaluate your findings before you do any formal statistical analysis. For that reason we suggest the following steps when you have some data ready to analyse:

  1. plot the data in an appropriate format. If you are comparing sample means then a box plot is best, especially if it shows the 95%CL of the means; for cause and effect (correlation, regression) make a scatter plot; to look at the distribution of data, make a histogram or bar graph
  2. evaluate the pattern by examining the plot and assessing whether there is a strong or weak effect. Are the differences between means likely to be biologically important? Does the independent (predictor, X-axis) variable have a strong effect on the dependent (response, Y-axis) variable? Is the distribution of data normal?
  3. perform the appropriate statistical analysis to answer the question of interest. See here for a guide to the kinds of analysis you might want to perform. See below for a simple guide to actually performing those analyses.
  4. interpret your results in light of step 3 and especially step 2, above. The P-value and/or confidence limits will give you some indication of the confidence you should have in the magnitude of the effects that you could see when you evaluated the pattern (step 2). When P≤0.05 we usually say that the results are statistically significant, and thus that we have reasonably good confidence that the size of the effect that we see is reasonably accurate. This does not mean that the effect is biologically (or economically, or medically) significant, as that is for you to decide.

Worked examples

On the pages listed below, we provide simple biological examples that walk you through some of the the steps listed above to give you a better idea as to what we are talking about.

Some simple statistical tests

On separate pages we provide some details and resources on how to perform and interpret the results of some simple statistical tests. Click on each procedure or test to go to its page.

I've spent more time than many will believe [making microscopic observations], but I've done them with joy, and I've taken no notice those who have said why take so much trouble and what good is it?

Antonie van Leeuwenhoek

It's a parts list... If I gave you the parts list for the Boeing 777 and it had 100,000 parts, I don't think you could screw it together and you certainly wouldn't understand why it flew

Eric Lander

What is true for E. coli is also true for the elephant

Jacques Monod

The world becomes full of organisms that have what it takes to become ancestors. That, in a sentence, is Darwinism

Richard Dawkins

Shall we conjecture that one and the same kind of living filaments is and has been the cause of all organic life?

Erasmus Darwin

Nature proceeds little by little from things lifeless to animal life in such a way that it's impossible to determine the line of demarcation


Cells let us walk, talk, think, make love, and realize the bath water is cold

Lorraine Lee Cudmore

In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history

Charles Darwin

It is my belief that the basic knowledge that we're providing to the world will have a profound impact on the human condition and the treatments for disease and our view of our place on the biological continuum

J. Craig Venter

Imagine a house coming together spontaneously from all the information contained in the bricks: that is how animal bodies are made

Neil Shubin

A grain in the balance will determine which individual shall live and which shall die - which variety or species shall increase in number, and which shall decrease, or finally become extinct

Charles Darwin

The stuff of life turned out to be not a quivering, glowing, wondrous gel but a contraption of tiny jigs, springs, hinges, rods, sheets, magnets, zippers, and trapdoors, assembled by a data tape whose information is copied, downloaded and scanned

Steven Pinker

We wish to discuss a structure for the salt of deoxyribose nucleic acid. (D.N.A.). This structure has novel features which are of considerable biologic interest

Rosalind Franklin

We are biology. We are reminded of this at the beginning and the end, at birth and at death. In between we do what we can to forget

Mary Roach

The systems approach to biology will be the dominant theme in medicine

Leroy Hood

I've always been interested in animal behavior, and I keep reading about it because it's so surprising all the time - so many things are happening around us that we neglect to look at. Part of the passion I have for biology is based on this wonderment"

Isabella Rossellini

Because all of biology is connected, one can often make a breakthrough with an organism that exaggerates a particular phenomenon, and later explore the generality

Thomas Cech

Nothing in Biology makes sense except in the light of evolution

Theodosius Dobzhansky

Biology is now bigger than physics, as measured by the size of budgets, by the size of the workforce, or by the output of major discoveries; and biology is likely to remain the biggest part of science through the twenty-first century

- Freeman Dyson

Nothing can be more incorrect than the assumption one sometimes meets with, that physics has one method, chemistry another, and biology a third

- Thomas Huxley