Important Maths Formulas of Statistics and Probability
Class Mark  
Class Size  Class size = upper limit – lower limit 
Range  Range = (Maximum value) – ( Minimum value) 
Empirical Formula  Mode = 3 Median – 2 Mean 
Mean  
Mean of Ungrouped Data  
Mean for n observations x_{1}, x_{2}, x_{3},...x_{n}  
Mean for a discrete series  
Mean of Grouped Data  
Direct Method  
Assumed Mean Method  
Step Deviation Method 
Median  
Median of Ungrouped Data: To find the median of an individual series, arrange the given numbers in ascending or descending order.  
Median, if the number of observations n is odd  
Median, if the number of observations n is even  
Median of Grouped Data 
Mode  
Mode of Ungrouped Data  It is the most frequently occurring observation 
Mode of Grouped Data 
Probability  
Probability of an Event  
· The Probability of a sure event is 1.
· The probability of an impossible event is 0. · The sum of the probabilities of all the outcomes of an experiment is 1. · For any event A associated to a random experiment, we have:
