WEEK 6 Flashcards
PROBABILITY AND DISTRIBUTION
The ‘Normal Distribution’ Key Features:
- Peak in the middle
-Tails off symmetrically at either side of the peak
-Bell shaped curve
What is the definition of ‘Skewness’:
- The extent to which your frequency histogram is lopsided rather than symmetrical
-Skew suggest data that deviates from a normal distribution
Types of Skewed Distributions
- positively skewed distribution: The peak is shifted to the left towards the low numbers
2.negatively skewed distributions: The peak is shifted to the right towards the high numbers
Bimodal: 2 peaks in a distribution
Multimodal: Two major peaks in a distribution
Kurtosis: Leptokurtic
-a measure of peak and flatness, or steep and shallowness
Leptokurtic: Higher kurtosis/ very peaked distribution
Kurtosis: Platykurtic
Lower kurtosis/ flat distribution
Kurtosis: mesokurtic
Between the two extremes of peakedness and flatness
What is the Floor and Ceiling Effect?
- Floor: when a measure produces most values near the bottom end of a scale
-Ceiling: when a measure produces most values near the top end of a scale
The Standard Normal Distribution
- Normal shaped distribution with a mean of 0 and a standard deviation of 1
- the total area under the curve is 1/ 100%
- To compare scores from different samples we convert our scores into standardised scores, known as Z scores
Z scores
Z score: tells us how many standard deviations above or below the mean a score is
- To calculate the z score, subtract the sample mean from the score and then divide by the sample standard deviation
Identifying Outliers using Box Plots
- SPSS identifies
- outliers with a o
-extreme scores
-Check for errors in data entry
-REPORT IT