Psyc 300-Module 15: Inferential statistics (Module 6 of Psyc 301) Flashcards
What is the difference between descriptive statistics and inferential statistics?
Descriptive statistics is summarizing or describing data from popylations and inferential stats is maing inferences from distributions (analyze samplings to make predictions about larger populations)
The normal distribution
Desccribes a very common probability distribution of values of a continous variable around the mean, no skew
Graph of a normal distribution is called
The normal curve
Vertical axis of the normal curve
Frequency of values
Horizontal axis of the normal curve
Scale of continous values, what we are measuring
Properties of a normal distribution (4)
- symmetrical
- unimodal
- bell shaped curve
- mean mode and median are equal
Spread of normal distribution is determined by—– larger spread means —–
standard deviation
larger SD
About —% of the data lie within 1 SD of the mean
68%
About —% of the data lie within 2 SD of the mean
95%
About —% of the data lie within 3 SD of the mean
99.7%
The standard normal distribution
A normal distribution with a mean of 0 and a standard deviation of 1
Properties of the standard normal deviation (2)
- The cumulative area is close to 0 for Z scores close to z=+/- 3.49
- The cumulaytive area increases as the Z score increases
Z-table
Table with pre-calculated areas under the curve up to each value for Z for a standard normal distribution
Standardization+formula (2)
Turning data into a standard normal distribution
- use the formula z=(x-mean)/SD
If you are trying to find the Z score for anything below the mean, your 2 scores should be
negative