Two-Way-Tables Wjec-Eduqas Higher

Two-way tables

What are two-way tables?

• Two-way tables are tables that compare two types of characteristics

  •  For example, a college of 55 students has two year groups (Year 12 and Year 13) and two language options (Spanish and German)

  • The two-way table is shown: 

    	Spanish	German
    Year 12	15	10
    Year 13	5	25

How do I find probabilities from a two-way table?

• Draw in the totals of each row and column

  • Include an overall total in the bottom-right corner

    • It should be the sum of the totals above, or to its left (both work)

  • For the example above:
     

    	Spanish	German	Total
    Year 12	15	10	25
    Year 13	5	25	30
    Total	20	35	55

• Use this to answer probability questions

  • If a random student is selected from the whole college, it will be out of 55

    • The probability a student selected from the college studies Spanish and is in Year 12 is

    • The probability a student selected from the college studies Spanish is

  • If a random student is selected from a specific category, the denominator will be that category total

    • The probability a student selected from Year 13 studies Spanish is