median

• the middle value-median
• discrete data:

  1.Put the numbers in order from smallest to largest.

  2.The median is the 1/2(n+1)th value-this means find your total frequency,add 1 to it and then divide by 2.The answer is not your median but the position your median will be in the list after being put in order.

  3.Find the median position from the list of values.This is your median value.If the median position is a decimal value such as 7.5 then you would find the 7th and 8th values in the list and then divide by 2.
• If data is in a frequency table,add the frequency values (like you would do with cumulative frequency) until you reach a row that includes the median position between it.the median is the category class that contains 1/2(n+1)th value.
• grouped data:

  fro grouped continuous data (has classes with the inequality symbols), the median is the 1/2th value.The median class is the class interval which contains the median position.sometimes you may be asked to work out an estimate for the median value rather than the median class.For grouped data your median will always be an estimate as you do not know exact values.
• estimate median using linear interpolation:

  1.Use 1/2 n to find the median position.

  2.Find Cumulative Frequency (CF) of the frequency column until you reach the class interval that contains 1/2th value.this is the group that contains the median.

  3.Find the median's position in the group and see how many more values you need in that class to get to the median.

  4.Divide the number by the frequency for the median class.

  5.Multiply your answer by the class width.

  6.Add your answer to the lower bound for the class interval.This is your estimate for the median value.