PSYC*1010 Chapter 6: Probability Flashcards
How is the probability of a specific outcome defined?
As a fraction, or proportion, of all possible outcomes
What is the notation for probability?
“Probability of event A” = p(event A)
How can probability be expressed?
- Fractions
- Decimals
- Percentages
How is probability most commonly expressed?
Decimals
All probability values are between ___ and ___
0 and 1
What does a probability of 0 indicate?
That the event is impossible/will not occur
What does a probability of 1 indicate?
That the event is certain/will occur
How are populations compared to samples?
Using probability
How are samples compared to populations?
Using inferential statistics
How is probability used in inferential statistics?
To predict the type of samples that are likely to be obtained from a population (estimates the connection between samples and populations)
What is percentile rank?
The percentage of individuals in the distribution with scores less than or equal to the specific score
When a score is referred to by its percentile rank, what is the score called?
A percentile
What does a random sample require?
That each individual in the population has an equal chance of being selected
What is a simple random sample?
A sample obtained from random sampling
What is the main difference between a simple random sample and an independent random sample?
- Simple random sample: result of random sampling WITHOUT replacement
- Independent random sample: result of random sampling WITH replacement
What is the additional requirement of independent random sampling?
The probability of being selected remains constant from one selection to the next if more than one individual is selected
How does the probability of being selected remain constant from one selection to the next if more than one individual is selected?
By returning each individual selected to the population before making the next selection (sampling with replacement)
Which type of sampling assures no bias?
Independent random sampling/sampling with replacement
Unless specified, which random sampling technique should be assumed as the method used?
Independent random sampling
T or F: When a population is presented in a frequency distribution graph, portions of the graph do not correlate to probabilities.
- False
- A particular portion of the frequency distribution graph corresponds to a particular probability in the population
T or F: Probabilities and proportions are equivalent.
True
What are the three main physical properties of a normal distribution?
- Symmetrical
- Single mode in the middle
- Frequencies tapering off toward either end of the distribution
What is the unit normal table?
A table listing proportions corresponding to each z-score location in a normal distribution
What is contained in column A of the unit normal table?
The z-score values corresponding to different position in a normal distribution
What is contained in column B of the unit normal table?
The proportion of scores in the body of the distribution
What is contained in column C of the unit normal table?
The proportion of scores in the tail of the distribution
What is contained in column D of the unit normal table?
The proportion of scores located between the z-score and mean of the distribution
What is the difference between the body and the tail of a distribution?
- Body: the larger portion of the distribution*
- Tail: the smaller portion of the distribution*
*Regardless of which side of the mean the proportion is on
What are two ways in which the unit normal table can be used?
- To determine proportions/probabilities for specific z-score values
- To find the location of a z-score corresponding to specific proportions
