Normal Distribution, Trends, Correlations and Hypotheses Flashcards
What is normal (Gaussian) distribution?
show a symmetric bell shape where mean, median and mode are similar or identical
How does normal distribution work?
values closer to the mean are more frequent and further are less frequent
How are standard deviations and normal distribution linked?
2/3 values fall into SD 1 and 95% in SD 1.96
What are Z-scores?
the individual observations of normally distributed data and how likely a sample point belongs to that data set
What do statistical tests aim to do?
Compare two mutually exclusive hypotheses
What are the 2 types of hypotheses?
Null
Alternative
What is the null hypothesis?
Assumes there is no difference, no correlation, etc. Apparent differences are just due to chance. Rejected if less than 5% likely (i.e. falls outside of 95% interval)
What is the alternative hypothesis?
Assumes significant difference, significant correlation
What can the correlation outcomes be of testing 2 variables?
Positive or direct correlation (both increase together)
Negative or inverse correlation (one increases as the other decreases)
no (obvious) correlation
What is the numerical measure for the degree of relationship between 2 variables?
Correlation coefficient = r = pearson correlation
What is the formula for standard deviation?
r = Sum of (X-(X mean))(Y-(Y mean))/ (n-1)/Sx X Sy
What is the coefficient of determination R*2?
measure of the proportion of variability in one variable in comparison to the other variable (extent of predictability)
How can the pearson correlation be exoressed?
Number between -1 to +1 with 0 being no correlation
How can R*2 be expressed?
0 to +1 with +1 being predictable without error
What does correlation not imply?
Causation
