Data Processing/Statistical Analysis Calculating Reaction Rates: This is a slope - just like in math class! rate = y = y 2 -y 1 Graphing: At least two ways to graph data: x x 2 -x 1

Data Processing/Statistical Analysis Write down a definition for each of the following: Mean Range Standard Deviation Error Bars

Data Processing/Statistical Analysis Check your work: Mean - average of data points Range - spread of data (difference between smallest and largest point) Standard Deviation - measure of spread of data around the mean (how tightly clustered the data are) Error Bars - represent variability of graphed data - can show range or standard deviation

Statistical Analysis If you are going to use a statistical test, you should state a null hypothesis. What is a null hypothesis? When would you use a correlation test (Pearson r value)? When would you use a t-test?

Null Hypotheses If you are going to use a statistical test, you should state a null hypothesis. What is a null hypothesis? A null hypothesis predicts no difference between your data sets. Ex. No correlation exists between dog size and hours of barking per day. There is no difference in coolness of left- handed and right-handed people.

Correlation When would you use a correlation test (Pearson r value)? To determine the correlation between two variables. Shortcuts in Excel: =PEARSON(array 1, array 2) =CORREL(array 1, array 2) How to interpret: StrongNo Strong negativecorrelation positive (Reject null)(Accept null) (Reject null) quick demo

Correlation r 2 is the coefficient of determination How to interpret: r 2 can be reported as a %, and tells you how much of the variance of one variable is accounted for by the other variable. Ex. If the correlation between dog size and amount of barking is r=.90 (strong positive correlation, reject null hypothesis), then r 2 =.81 This means that 81% of the variation in barking can be accounted for by dog size. You could make a good prediction of barking based on size.

t-Test When would you use a t-test? To compare the means of two data sets. Shortcuts in Excel: =TTEST(array 1, array 2, tails, type) **tails=2, type=2 How to interpret: If p>0.05, Accept the null hypothesis There is no significant difference between data sets. If p<0.05, Reject the null hypothesis There is a significant difference between data sets. quick demo

t-Test How to interpret: If p>0.05, Accept the null hypothesis There is no significant difference between data sets. If p<0.05, Reject the null hypothesis There is a significant difference between data sets. Ex. Null hypothesis: There is no difference in coolness of left-handed vs right-handed people. If p= will you accept or reject the null hyp? …..is there a significant difference in coolness? Review

Wiki Resources What page and topic will you find the “Excel Stats Activity” and “Topic 1 Notes” on? IB DP Biology SL, Topic 1 How might these resources help you with your IA?