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Flashcards in Statistics 2 Deck (21)
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1

What is the equation for the product moment correlation coefficient?

r = sxy/square root of (sxx)(syy)

2

What are the conditions for a PMCC?

Population must be bivariate normal
Data from a random sample
Bulk of data should form an ellipse on a scatter diagram

3

Hypothesis test for PMCC

H0:r=0
H1: r>0, r<0, r not equal 0
if r is bigger than or equal to the critical value reject H0

4

Spearman's rank equation

rs = 1 - 6sumd^2/ n(n^2 -1)

5

Spearman's hypothesis

H0: no association
H1 : positive association, negative association, some association
If rs is greater than the critical value reject H0

6

What is PMCC?

measures how close to a straight line the points on a scatter graph lie, if r=0 no correlation

7

How do you work out line of regression?

y = a + bx
b = sxy / sxx
a = y bar - b x bar

8

Equation for residuals

observed y value - expected y value
positive - line is too low
negative - line is too high

9

What is interpolation and extrapolation?

Interpolation - reliable- within data set
Extrapolation - out of data range - not reliable

10

Poisson distribution equation

x - p (lamda)
P(X =r) = e^-lamda x lamda^r / r!

11

Conditions for poisson

Random, independent and at a fixed rate of occurrence
mean is roughly equal to the variance

12

Normal distribution

X - N(mean , standard deviation squared)
z = x-mean / standard deviation

13

Normal hypothesis test

H0: mean = k
H1: mean >k, mean
x - N(mean, standard deviation squared/n)
z = sample mean - mean / (standard deviation/square root of n)

14

Estimating variance

n/n-1 [(sum x^2/n) - (sum x/n)^2)]

15

Chi-squared equations

expected = row total x column total/ overall total
X^2 = (o-e)^2 / e
v = (row-1) (column-1)

16

Chi-squared hypothesis

H0: no association
H1: some association
X^2 is greater than the critical value, reject H0

17

Approximating
Binomial to poisson

X - B(n,p) -----------------> X - P(np)
n is large
p is small

18

Approximating
Poisson to normal

X - P(lamda) --------------> X - N(lamda, lamda)
lamda is bigger than 10
continuity correction

19

Approximating
Binomial to normal

X - B(n,p) ------------> X - N(np, npq)
n is large
p is roughly 1/2

20

What is a continuity correction?

make the equal to group 0.5 bigger

21

What is the assumption for chi squared?

Independent