Formulas Statistics Period 1 Flashcards
What is the Interquartile Range?
Range of values between the first and the third quartile of your dataset (25th-75th percentile)
Calculation: IQR=Q3-Q1
What is the standard deviation Sx?
Describes by how much all the values of a dataset differ from the mean on average.
Calculation: Square root of the variance.
What is variance?
Average squared deviation.
Calculation: take square of deviation (sum of all values - mean) and then divide by number of subjects - 1 (n-1)
What is Centering?
Values are changed but not the scale, to to make the data more managable.
Calculation: X’ = X - X-mean
What is Standardizing?
Values and the scale are transformed to make the data more managable.
Z-Score: Z = X - X-mean / Sx
Correlation coefficient r
rxy = sum of Zx*Zy / n-1
Regression coefficient b (slope of regression line equation)
b = rxy * Sy / Sx
Intercept of regression equation
a = Y-mean - bX-mean
Explained variation in regression-analyses
squared sum of y-expected - y-mean
Unexplained (error) variation in regression analysis
Unexplained sum of squares divided by total sum of squares.
Squared sum of y - y-expected
Proportion explained variation
Explained sum of squares divided by total sum of squares.
rxy^2
Total sum of squares
Sum of explained sum of squares and the unexplained (residual) sum of squares.
Interrater reliability
Level of agreement between raters.
observed agreement - expected agreement / number of judgements - expected agreement
Regression line
y-expected = b (slope) *x + a (intercept)
What is the Standard deviation Sx?
Describes by how much all the values differ from the mean on average.
Calculation: Square Root of the variance.
