# Topic 1 - Statistical Analysis

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1. What are error bars for?
They are a graphical representation of the variability of the data
2. What is standard deviation for?
Summarize the spread of values around the mean. 68% of the values fall within one SD of the mean.
3. How much data falls within 2 SD of the mean?
98%
4. What does a small standard deviation mean?
Data is clustered around the mean value.
5. What does a large standard deviation mean?
There is a wider spread around the mean.
6. What does the t-test do?
• It uses the standard deviations of both sets of data to deduce the significance of the difference.
• It helps scientists work out if the difference is significant or not.
7. What are the 'degrees of freedom' if you have 2 samples, both with a population of 10?
• Degrees of freedom are the sum of the samples ize of each of the two groups minus 2.
• For example, if two groups of 10 plants each are being looked at, then 10 plus 10 is 20 minus 2 is 18. Thus, the number to look at in the ‘Degrees of freedom’ column is 18.
 Author: ENason ID: 130972 Card Set: Topic 1 - Statistical Analysis Updated: 2012-05-04 12:44:08 Tags: IB DP BIO STATISTICS Folders: Description: IB DP BIO - STATISTICS Show Answers: