Probability and Significance, and Sign Test

• What does a probability of 0 indicate?

  Statistical impossibility
• What does a probability of 1 indicate?

  Statistical certainty
• What does significance in statistics tell us?

  It indicates how sure we are that a difference or correlation exists
• What does the experimental hypothesis indicate?

  It suggests that there is a difference or correlation between variables
• What is the null hypothesis?

  It states that there is no difference between the conditions
• If Miss Hall has a 0.05 chance of rain over 100 days, how many days is she likely to get wet?

  5 days
• What is the significance level commonly used in psychology?

  0.05 (5%)
• What does P<0.05 mean?

  The probability that the result occurred by chance is equal to or less than 5%
• Why can we never be 100% certain in psychological tests?

  Because there is always a chance that results occurred by chance
• When might a researcher use a significance level of P<0.01?

  When findings may raise ethical dilemmas or have high theoretical value
• What is the purpose of the sign test?

  To determine whether a difference is statistically significant
• When should the sign test be used?

  When looking for a difference rather than an association
• What type of data is required for the sign test?

  Nominal data
• What does the sign of difference indicate in the sign test?

  It tells you who remembered more in each condition
• How do you find the less frequent sign (S) in the sign test?

  By counting the number of + signs and - signs
• What is the critical value used for in statistical tests?

  To determine whether to reject the null hypothesis
• What does the Rule of R state?


  If the statistical test's name has an R in it, the calculated value must be more than or equal to the critical value
• What happens if the calculated value is higher than the critical value?


  The findings are not significant
• What is a Type 1 error?

  A false positive where the null hypothesis is rejected incorrectly
• What is a Type 2 error?


  A false negative where the null hypothesis is accepted incorrectly
• When is a Type 1 error more likely to occur?

  When the significance level is set at p = 0.1
• When is a Type 2 error more likely to occur?


  When the significance level is set at p = 0.01
• What is the significance of Damien's calculated value of p=0.3 regarding his grandmother's memory test?

  It indicates a Type 2 error as he failed to reject the null hypothesis
• What type of error is indicated by a probability value of 0.12 in a memory test?

  Type 2 error, as the null hypothesis was not rejected
• What does the letter N stand for in relation to statistical tests?

  N stands for the number of participants in the study
• What is the difference between the calculated value of S and the critical value of S?

  The calculated value of S is derived from the data, while the critical value of S is determined from statistical tables
• How do you convert 5% to a decimal?

  0.05
• When is the sign test used?

  When looking for a difference between two related conditions
• What are the steps to use a critical value table?

  1. Determine if it is a one-tailed or two-tailed test.
  2. Identify the number of participants (N).
  3. Check the level of significance (p value).
• What are the strengths and weaknesses of using a significance level of p = 0.05?


  Strengths:

  • Commonly accepted in psychology
  • Balances Type 1 and Type 2 error risks

  
  

  Weaknesses:

  • 5% chance of Type 1 error
  • May not be stringent enough for critical research
• What are the implications of using a significance level of p = 0.01?

  • More stringent, reducing Type 1 error risk
  • Increases likelihood of Type 2 errors
  • Suitable for high-stakes research (e.g., medical trials)
• What are the implications of using a significance level of p = 0.1?

  • Higher risk of Type 1 error
  • Less conservative, may lead to false positives
  • Not recommended for critical research
• What are the criteria for using the sign test?

  • Looking for a difference, not an association
  • Repeated measures design
  • Data should be nominal
• What is the relationship between calculated value and critical value in statistical tests?

  • Calculated value is derived from the data
  • Critical value is determined from statistical tables
  • Comparison determines significance of results
• What are the potential errors in hypothesis testing?

  • Type 1 Error: Rejecting null hypothesis incorrectly
  • Type 2 Error: Accepting null hypothesis incorrectly
• What is the significance of the calculated value in hypothesis testing?


  • Indicates the result of the statistical test
  • Compared to critical value to determine significance
• What is the importance of practicing inferential statistics?

  • Helps in understanding statistical concepts
  • Prepares for exam questions
  • Builds confidence in applying statistical tests