Key Takeaways

• When we say their is a significant difference between two groups, we mean that the probability of seeing that difference by chance is less than or equal to 5%.

• Most statistical tests rely on 3 factors to decide whether a difference is significant:

  • How big is the difference between the groups?

  • How many people or observations were sampled?

  • How much variation was there between the people in the groups?

• Remember, statistics only tell you if there is a difference between your groups, not what caused that difference.  You must rely on your study design to determine the cause of the difference.