Formulas Flashcards
1
Q
Proportion
A
Number of cases / total sample size
2
Q
Mean
A
Sigma-x / n
3
Q
Median (even number)
A
(n/2)th, (n/2 + 1)th
4
Q
Median (odd number)
A
(n+1 / 2)th
5
Q
Standard Deviation for sample
A
Square root of: Sigma (x-xbar)squared / n-1
6
Q
95% Rule
A
(xbar-2s, xbar+2s)
7
Q
Z-score
A
x-xbar / s
8
Q
IQR
A
Q3 - Q1
9
Q
Finding small outliers
A
Q1 - 1.5(IQR)
10
Q
Finding large outliers
A
Q3 + 1.5(IQR)
11
Q
Standard deviation estimator (<70)
A
Range/4 or Range(1/4)
12
Q
Standard deviation estimator (>70)
A
Range/6 or Range (1/6)
13
Q
Regression line
A
yhat = a+bx
14
Q
Residual
A
y - yhat
15
Q
Least Squares line
A
Minimize Sigma(y-yhat)squared
16
Q
Interval estimate to find parameter
A
Statistic +/- margin of error
17
Q
95% confidence interval
A
Statistic +/- 2*SE
18
Q
Margin of Error
A
2*SE
19
Q
Standard deviation for population
A
Square root of: Sigma (x-xbar)squared / n
20
Q
Deviation
A
x-xbar
