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Why does Example 1 lead to accepting the null hypothesis?

In Example 1, there is a lot of variation within each group but not much variation between the groups. Because most of the difference is due to the people rather than the drink, the video concludes that the drink did not make much of a difference, leading to accepting the null hypothesis.

Conditions

  • The displayed Example 1 data are used.
  • Within-group variation is much larger than between-group variation.

Reasoning, step by step

  1. Inspect the spread inside each column to see large within-group variation.
  2. Compare the overall appearance of the three groups to each other to see small between-group variation.
  3. Conclude that most of the difference is due to the people rather than the drink.
  4. Accept the null hypothesis that the type of drink does not have any effect on reaction time.

Example

Water group: 10, 12, 18, 24, 36. Juice group: 11, 14, 19, 23, 38. Coffee group: 12, 13, 17, 25, 37. Conclusion text: "it's the people that make the difference, not the drink."

Common misconceptions

  • Assuming that because the numbers vary a lot overall, the groups must differ meaningfully.

Watch the explanation

1:11 – 1:46Watch this moment ↗

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.