Probability and Significance

• What does the term significance refer to in statistics?

  It indicates how sure we are about a correlation or difference existing.
• What happens if a result is found to be significant?

  We reject the null hypothesis and accept the alternative hypothesis.
• What does the null hypothesis (H0) state?

  There is no difference or correlation between the conditions.
• What does the alternative hypothesis (H1) state?

  There is a difference between the conditions.
• How is probability defined in statistics?

  It is a calculation of how likely it is for an event to happen.
• What is the range of probability values?

  From 0 (statistical impossibility) to 1 (statistical certainty).
• What is the usual level of significance in psychology?

  0.05.
• What does a p-value of 0.05 indicate?

  The probability of the difference being due to chance is 5% or less.
• What confidence level do researchers have in their results when the p-value is 0.05?

  Researchers have a 95% confidence level in their results.
• What is the p-value set at when there is a risk attached to the research?

  0.01 (1%).
• What are Type I and Type II errors in statistical testing?

  • Type I error: Incorrect rejection of a true null hypothesis (false positive).
  • Type II error: Failure to reject a false null hypothesis (false negative).
• What is a Type I error?

  It is the incorrect rejection of a null hypothesis that is actually true.
• What is a Type II error?

  It is the failure to reject a null hypothesis that is false.
• What does a Type II error imply about the research findings?

  Researchers claim there is no significant difference when there actually is one.