Lecture 5 Flashcards
What can frequency distributions be linked to?
Probability
How do you calculate relative frequency/ probability in frequency distributions?
Frequency/ N
Define skewness in terms of distribution
Deviation from symmetry. If data is skewed, the median is larger than the mean, if its not, than the mean is bigger than the median.
How can you reduce skewness?
transformations
Define modality in terms of distibution
Number of major peaks in a distribution - unimodal/ bimodal
Define kurtosis in terms of distribution
Peakedness of distribution - steepness. Either platykurtic, mesokurtic or Leptokurtic
What is platykurtic distribution?
Shallow, long distribution
What is mesokurtic distribution?
Normal distribution
What is leptokurtic distribution?
Very steep and narrow distribution
What are the key features of normal distribution?
- Asymptotic - Lines dont touch axis
- Symmetrical around the mean
- mean = median
- More observations close to the mean, fewer the further out you go
What does asymptotic mean?
Lines dont touch axis
What is a Z score
A standardised score, regardless of measurement variable that reflects the number of SD’s an observation is away from the mean.
How do you calculate the z-score
(obersvation-mean) - SD
What does a postive and negative z-score represent?
Positive score is above mean, negative is below the mean
What does that area under a probability density curve always equal?
1
