## Probability, Significance and Type Errors

Teachers or students who want the original PPT or resources referred to please tweet @psychopepper

### Learning Objectives

- To
**KNOW**and**UNDERSTAND**what probability and significance is in Psychology. - To
**KNOW**and**UNDERSTAND**what type errors are in Psychology. - To
**APPLY**knowledge of aims to past exam questions

### Lesson Outline:

#### Tasks:

- What is the probability of drawing an ace of hearts from a pack of cards?
- What is the probability that everything I have taught you this year is wrong?
- Take notes on what probability and significance mean
- Work out what p<0.05 means
- Convert decimals to fractions
- Discuss and take notes on what significance means in psychology and which significance levels are used when and what impact they have.
- Discuss and take notes on type errors, finding a method of understanding that works for you. Attempt questions on type errors to check understanding.

#### Content Recap

**Probability:** A numerical measure of the likelihood that certain events (or behaviour) will occur

**Significance:** a statistical term indicating the findings are sufficiently strong for us to accept the research hypothesis and conclude the result were not by chance. The significance level that a psychologist chooses is the highest **probability** that their results are wrong that they are willing to accept. If I choose *p*≤0.05 then I am willing to accept a 5% chance that my results are wrong (due to chance). If I choose *p*≤0.01 then I am only willing to accept a 1% chance that my results are wrong (due to chance). And if I choose a *p*≤0.10 then I am willing to accept a 10% chance that my results are wrong (due to chance)

**A type one error **is a correct assumption that is mistakenly rejected, therefore rejecting the null hypothesis when is true. It is a **false POSITIVE**; and **P **has **single** vertical line… A Type I error can be viewed as the error of excessive trust. Another way of thinking about it is that an investigator may be “crying wolf” (raising a false alarm) without a wolf in sight (*H*0: no wolf).

**A type two error **is a false assumption that is mistakenly accepted, therefore accepting the null hypothesis when is false. It is a **false NEGATIVE**; and **N **has **double** vertical lines… A Type II error can be viewed as the error of excessive doubt. Another way of thinking about it is that an investigator may fail to “cry wolf” (doesn’t raise the alarm) when a wolf is really there (*H*0: no wolf).

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#### Study Notes:

If you would like to download a set of study notes for this lesson, you can do so here (tba). If you would like access to the original word file please tweet @psychopepper

#### Textbooks or extra reading:

I would suggest that you have a copy of one of the textbooks which will allow you to read around the subject matter, pre-read ahead of lessons or even take extra notes/practise questions afterwards. I would recommend the following (you do not need to replicate books, one of each type is plenty!)

- Psychology for A Level:
- Textbooks affectionately known as green hair girl (Year 1) pink hair girl (Year 2)
- Revision Guides affectionately known as green hair girl (Year 1) pink hair girl (Year 2)

- Complete Companion Series:
- Textbooks affectionately known as catbook (Year 1) dogbook (Year 2).
- Revision Guides affectionately known as kittenbook (Year 1) puppybook (Year 2).
- Exam Companions also affectionately known as kittenbook (Year 1) puppybook (Year 2).
- Research Methods guide

- CGP