Chapter 6: Probability Flashcards
how is probability determined?
determined by a ratio comparing the frequency of occurrence for that outcome relative to the total number of possible outcomes
how is probability expressed?
as a proportion, fraction, or percentage
why do we use probability?
to relate the population back to samples
what is the most common z-score
0
what is the least common z-score
± 3
Probability of picking a score within one standard deviation of the mean
0.68
Probability of picking a score within two standard deviations of the mean
0.95
Probability of picking a score within three standard deviations of the mean
0.997
Column A of the unit normal table
lists z-score values.
column B of the unit normal table
body of the distribution
column C of the unit normal table
tail of the distribution
column D of the unit normal table
the proportion between the mean and the z-score location.
How do you find the probability corresponding to a particular score? (X)
- Transform the score into a z-score
- Look up the z-score in the table and read across the row to find the appropriate proportion/probability
How do you find the score corresponding to a particular proportion?
- Look up the proportion in the table
- Read across the row to find the
corresponding z-score - Transform the z-score into an X value.
The proportions of positive and negative values of a specific z-score
are the same
proportions are always ___
positive
tail of the distribution of a negative z-score is
on the left
tail of the distribution of a positive z-score is
on the right
random sampling
each person had an equal chance of being in the sample
independent and random sampling
each person in the sample had an equal chance, and once someone is in the sample, it doesn’t influence someone else’s chance of being in the sample
are indepedent random samples drawn with replacement?
yes
The percentile rank for a score in a normal distribution
the proportion to the left of the score.
