Summary OCR A level Biology A Student Book 2 ActiveBook - Statistics cheat sheet

‭Statistics‬ ‭statistical tests‬
‭Spearman's rank correlation coefficient‬
-‭ > the strength and direction of relationship between measurements of two‬
‭variables‬
‭●‬ ‭the value of r‬‭s‬ ‭is always between +1 and -1, when‬‭the rS value‬
‭exceed critical value then reject null hypothesis‬
‭●‬ ‭degree of freedom= number of data- 1‬




‭Unpaired t test‬
‭-> the significance of differences between means of different set of data‬
*‭ *value > critical value = the correlation is significant, reject null hypothesis‬ ‭●‬ ‭degree of freedom= n1+n2 - 2‬
‭**value < critical value = the correlation is significant, reject null hypothesis‬ ‭n1 = number of data in sample 1‬
‭**the lower the percentage, the more certain that the data did not arise due‬ ‭n2 = number of data in sample 2‬
‭to chance‬
‭mean‬
‭-> the average value of the set of data‬
‭mode‬
‭-> the most frequently occurring value in the set of data‬
‭median‬
‭-> the middle value of the set of data‬
‭standard deviation‬ ‭1.‬ ‭calculate the value of t, then compare to the value to critical value‬
‭-> shows how far the data is from the mean‬
‭●‬ ‭the smaller the deviation, the closer the value to the mean‬
‭Paired t test‬
‭-> the mean difference of 2 observations in the‬‭same‬‭sample‬