S1 Flashcards
How do you work out the median for continuous data?
N/2
Use interpolation to find the value of the corresponding term.
How do you work out the median for discrete data?
N/2
If n is not a whole number, round the number up and pick the corresponding term.
Mean of continuous data?
Sum of fx/ sum of f
Variance equation?
(Sum of x/n) squared
Standard deviation = ?
Square root of variance.
Variance for frequency table or grouped frequency distribution?
((Sum of fx/sum of f)squared)
What is the addition rule:
P(A u B) = ?
P(A) + P(B) - P(A n B)
Conditional probability:
P(A given B) = ?
P(A n B) / P(B)
Multiplication rule:
P(A n B) = ?
P(A|B) x P(B) or the other way round.
Independent if?
P(A|B) = P(A) or other way round
P(A n B) = P(A) x P(B)
Mutually exclusive rule?
P(A n B) = 0
How do you find the mean of a combined set of data?
n1xbar1 + n2xbar2 / (n1 +n2)
What information can be used to decide if a distribution is skewed?
Quartiles
Shapes of box plots
Formula:
3(mean-median) / standard deviation (larger value = larger skew)
Sxx/Syy = ?
Sum of x^2 - (((sum of x)^2) / n)
Sxy = ?
(Sum of x times sum of y) / n
r = ?
Sxy / root(SxxSyy)
What does r measure?
Linear relationship
r=1
Perfect +ve linear correlation
r=-1
Perfect -ve linear correlation
r=0
No linear correlation
What is the line of regression for y on x?
y = a + bx
b = Sxy / Sxx
a = ybar - bxbar
What is extrapolation and interpolation?
Interpolation = when you estimate the value of a dependent variable within the range of the data. Extrapolation = ""outside the range of the data.
DRV
What is x and X?
x is a particular value of X.
DRV
What does P(X=x) or p(x) refer to?
It refers to the probability that X is equal to a particular value x.
DRV
Equation for cumulative frequency distribution?
F(x) = P(X=<x)
DRV
What is E(X) equation?
Sum of xP(X=x)
DRV
Variance of X = ?
E(X^2) - [E(X)]^2
DUD
What are the condition for a discreet uniform distribution?
- A DRV X is defined over a set of n distinct values.
- Each value is equally likely.
DUD
E(X) = ?
(n+1) / 2
DUD
VAR(X) = ?
(n+1)(n-1) / 12
S1 questions:
Paper B
Q 1, 3, 4
Area of bar =
k x frequency
Frequency density =
Frequency/class width