Inferential Statistics Flashcards
What are inferential statisitcs?
- When we make inferences about whole populations based on the sample taken from that population
- Allow psychologists to draw conclusions- these are based on the probability that a particular pattern has arisen by chance or not
What is the difference between inferential statistics and descriptive statistics?
Descriptive Statistics:
- Describe patterns or trends in a data set
- e.g. relationship, spread of scores (range & standard deviation) or may descirbe averages (measures of central tendancy, mean,mode,median)
- They cannot tell you if there is a significant difference- inferential statistics can
What is the certainty level that psychologists work at?
- 95%/ 0.05
- They are 95% certain that the results they have obtained are not due to chance or an unknown error
Therefore, there is a 5% probability that the results are due to chance/ unknown error
What is the level of certainty/acceptance known as?
Known as the probability/ significance level - it is called ‘p’
The 5% level is recorded as p=0.05 or p<0.0.5
What level do psychologists use when they want to be more certain?
- Researchers will use a stricter probability, such as p=0.01
- This means they are 99% certain their results were not due to chance
- The significance level is therefore 0.01/ 1%
Psychologists may use this when they are conducting studys of the effects of a new drug (can’t afford to have 5 people die/ experience extreme side effects, so they reduce it down to 1) By repeating the study
What is a type Ierror?
- False positive, accept the alternate/experimental hypothesis in error
- Means saying there is a difference or relationship between two variables but this is not true
- Significance level is too strict
What is a type II error?
- False negative, accept null hypothesis in error
- Means saying there is no difference in relationship when actually there is
What are the three levels of measurement? And explain what they are.
Nominal data:
- When looking at categories
Ordinal data:
- When you have a scale and rank information into order
Interval data
- When you have an objective scale with regualr intervals (often the best option)
What are the 8 tests used in inferential statistics?
- Sign test
- Chi squared test
- Wilcoxon
- Mann Whitney U
- Spearmans Rho
- Related T- Test
- Unrelated T- Test
- Pearson’s R
What does a test of difference or association refer to?
‘Test of difference’- Refers to experiment
‘Test of association’- Refers to correlation
What does a related or unrelated design refer to?
- ‘Related’- Relates to exp design being repeated measures or matched pairs
- ‘Unrelated’- Independant groups design
What does the type of data refer to?
- ‘Type of data’- Refers to levels of measurement (nominal, ordinal, interval)
LEARN TABLE IN STAT BOOKS
How do you know whether a hypothesis is direction or non-directional?
- Directional- Previous research has been carried out before
- Non-directional- There hasnt been previous research
What does the letter N mean in statistics?
‘N’= Number of participants
‘Na’= Number of participants in group A
‘Nb’= Number of participants in group B
What type of test is the sign test?
- Test of difference
- Related design
- Nominal data
