Probability and Significance

• What do researchers begin their investigations by writing?

  A hypothesis
• What are the two types of hypotheses?

  • Directional hypothesis
  • Non-directional hypothesis
• Which type of hypothesis is: "Students who take notes manually by pen and paper will score higher on exams than those who take notes on laptop"?

  Directional hypothesis
• Which type of hypothesis is: "There will be a difference in people’s mood when it rains compared to when it is sunny"?

  Non-directional hypothesis
• Which type of hypothesis is: "People who eat more vegetables daily will score higher on IQ than people who do not"?

  Directional hypothesis
• Which type of hypothesis is: "Students who study Psychology are happier than students who study Accounting"?

  Directional hypothesis
• Which type of hypothesis is: "After drinking 300ml of Red Bull, participants say more words in the next 5 mins than participants who drink 300ml of water"?

  Directional hypothesis
• What is an alternative hypothesis also referred to as?

  H1
• What does the null hypothesis state in the context of the Red Bull experiment?

  No difference in words spoken
• What does probability (p) represent?

  The likelihood of an event occurring
• What is the usual level of significance in statistical tests?

  0.05
• How is the level of significance properly written?

  p ≤ 0.05
• When is a 0.01 significance level typically used?

  When more confidence is needed
• In what situations might a 0.01 significance level be preferred?

  Controversial findings or ethical dilemmas
• What is a Type 1 error?

  A false positive
• What happens in a Type 2 error?

  Null hypothesis is kept incorrectly
• What type of error did Damien make regarding his Gran's memory test?

  Type 2 error
• When is a Type I error more likely to occur?

  If the significance level is too high
• When is a Type II error more likely to occur?

  If the significance level is too low
• What are the criteria for finding the correct critical value in statistical tests?

  1. Hypothesis type (one-tailed or two-tailed)
  2. Number of participants or degrees of freedom
  3. Level of significance (p value)
• Why might a 0.01 level of significance lead to a Type 2 error?

  It may be too strict for many experiments
• When would a 0.01 level of significance be preferred?

  When findings are controversial or ethically important
• How can one check for a Type 1 error?

  Repeat the experiment and compare findings
• What is the difference between Type 1 and Type 2 errors?

  • Type 1: False positive, rejecting null hypothesis incorrectly
  • Type 2: False negative, keeping null hypothesis incorrectly