# Statistics

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Statistics deals with description and analysis of data that can vary.

Statistics is particularly useful in biology because individuals vary even within the same species; any given biological characteristic varies between the individuals. That is why the term ** a variable** is used for a characteristic.

In general the purpose is to study a * population* of individuals that fulfill certain criteria. Usually, however, it is impossible to investigate the whole population in question. Instead one would confine the investigation to a

*of the population. A sample should be a*

**sample***selection of individuals from the population of interest. Otherwise extrapolation of the findings in the sample back to the population would be unreliable or biased.*

**random**The *variation between individuals* must be taken into account in the description and analysis of the data. Statistics can describe variation and compare groups of individuals using methods that involves probability theory. Statistics also deals with collection, analysis, interpretation and presentation of observations, which are numeric or can be converted into numerical data.

This part of the website deals with description of raw data, probability distributions, tests to detect differences (significance tests), estimation of confidence intervals and calculation of the number of subjects needed for a certain investigation (power calculation).

### Online Computing

In each of the pages in this section of the website you can find links to pages, where you can perform the calculations online – in most cases just by copying and pasting the data e.g. from a spreadsheet program like Excel.

### PROGRAM to convert decimal commas to decimal points

In most cases the numbers need to have a decimal point to use the online facilities. If your numbers have a decimal comma (which is the case in some countries), you will need to replace the commas with decimal points.

For that you can use the Windows program, which you can download below. I have made the program, which is very small and guaranteed free of any virus. When unzipped you can use it.

You copy the data you need and paste them to the program. You let the program replace the commas with points and then you can paste the converted numbers directly to the online calculation page. You can also save the converted numbers in a CSV (comma-separated values) file format, which some of the online calculation pages need for input. Good Luck!