1. Statistical Analysis (2 hrs)
Objectives
1.1.0 Use significant figures for all calculations [this is an implied requirement]
1.1.1 State that error bars are a graphical representation of the variability of the data.
* Note that error bars can represent range of data -or- the standard deviation [see Click4Biology on "Why use one or the other?"]
* Keep in mind you will need a reasonably large sample of measurement to get an sd, so if you don't have a lot of repetition or samples for one independent variable then you should probably choose error bars to represent the range of your data
* If you choose error bars to represent range of data, make sure they include the range of your data AND experimental error. [ex. if your data range is 3 mL - 7 mL but your experimental error is ±1 mL, then the error bars should be at 2mL and 8mL.]
1.1.2 Calculate the mean and standard deviation of a set of values.
* WIth a given set of data, determine the mean and standard deviation.
* Explained on <http://en.wikipedia.org/wiki/Standard_deviation>
* [The following is from <http://answers.yahoo.com/question/index?qid=20081127214955AAMzvgF>
1. Find the normal mean. ( ∑n/n)
2. Find the differences of each number from the mean. (x-n)
3. Square these differences and add them together. (
4. Finally, divide by the number of terms.
o Ex. find the standard deviation of 2,3,5,6.
o 4 is the mean
o 4-2 = 2^2 = 4
o 4-3 = 1^2 = 1
o 4-5 = (-1)^2 = 1
o 4-6 = (-2)^2 = 4
o 4+1+1+4 = 10
o 10/4 = 5/2
o 5/2 is the standard deviation.
1.1.3 State that the term "standard deviation" is used to summarize the spread of values around the mean and that 69% of values fall within 1 sd.
* Describe difference between sd of a sample (s) and sd of a population (∂)
1.1.4 Explain how the standard deviation is useful for comparing the means and the spread of data between two or more samples.
1.1.5 Deduce the significance of the difference between two sets of data using calculated values for t and the appropriate tables.
1.1.6 Explain that the existence of a correlation does not establish that there is a causal relationship between two variables.
Perhaps one of the first things to do before going further is to go to Click4Biology's Statistical Analysis page and scan over the information there. [We will refer and use a number of off-wiki resources which have been well developed by other DP Biology teachers so book mark these sites in your own browser as we come to them.]