Chapter 7- Theoretical Distributions including the Normal Distribution Flashcards
Empirical distributions
Distributions using observed scores (i.e. real scores)
What are theoretical distributions based on?
Mathematical formulas and logic, rather than on empirical observations
What can you use theoretical distributions to find?
Probability
What does probability range from?
Probabilities are often called “chances in a hundred.”
It ranges from 0.00 to 1.00
What is the significance of 0 and 1 concerning a probability?
- 00- equals no certainty
1. 00- equals certainty
Rectangular distribution
distribution in which all scores have the same frequency.
It involves straight lines
Are straight lines still called curves?
Yes. The line that encloses a histogram or frequency polygon is called a curve, even if it is straight.
What do the areas of a probability add up to?
1.00
Binomial distribution
Is another example of a theoretical distribution.
Distribution of the frequency of events that can have only two possible outcomes
Example of a binomial distribution
Flipping a coin in the air. Finding the possibilities of heads/tails
How to calculate a binomial distribution
Multiply the probabilities of each of the independent events
Theoretical v empirical
Theo
- distribution may not reflect ‘exactly’ what happens
- best estimate of how events would actually occur
Empirical
- actual results influenced by chance
- if we redid the test and did 520, 5,200, or 52,000 the theo and empirical would sit flat on top of each other and match
Normal distribution
A bell-shaped, theoretical distribution that predicts the frequency of occurrence of chance events
Is your data wrong if it does not look like a normal distribution?
NO. Just because it’s not normal doesn’t mean it’s abnormal
What is the x-axis of a normal distribution?
z scores
