Key Vocabulary
   Median
   Mean
   Mode
   Modal class
   Range
   Statistics
   • When we gather data, we end up with a mass of 
   numbers.
   • These numbers, by themselves, are meaningless
   • They gain meaning when we perform calculations 
   on the numbers, creating statistics.
   Types of statistic
   • There are 2 types of statistic which are more important 
    than any others
   • Whenever we are asked to describe a population or to 
    compare two populations, we always use both of these 
    types of statistic
   Averages -mean, mode and median
   Measures of spread -range
   We are going to be looking at finding these statistics from 
   grouped frequency tables
   Types of average
   • Mode
     The value that occurs most often in the data.
    
   • Median
     Put the data in order.  The median is the
     middle value.  If there are two middle values, take
     the mean average of the two.
   • Mean
     Add all the numbers together and divide by
     how many numbers there are. 
   Example
   The following shows the weekly wage of a sample of 
   some professional footballers
   We are going to calculate an estimate of the mean, 
   an estimate of the median, and find the modal class.