maths unit 3 Flashcards
what is univariate data
the study of only one variable
what is bivariate data
the study of two variables at the same time to determine if there is a relationship that exists between them + how this relationship can be used to make predictions
what do you talk about when describing relationships in scatterplots
- the form - is it linear or non-linear
- the direction - is it positive or negative
- the strength - strong, moderate, weak
- possible outliers
what do dif letters mean in pearson’s correlation coefficient
n = no. pieces of data
xi = x - value (explan)
yi = y value (resp)
sx = stan dev. x-values
sy = stan dev. y - values
- and then the means
what to put in pearson’s correlation coefficient table
- stuff in first set of brackets
- stuff in second set of brackets
- then multiply by each other
what form. for equation of a line
y = mx + c
m = gradient (y2-y1/ x2-x1)
c = y-int
least squares regression line form.
y = a + bx
y = response variable
x = explanatory
b = gradient of the line (r x sy/sx) (r = corel. coefficient)
what to do in least squares reg line when explanatory variable is equal to 0
value of response variale is indicated by the y - intercept
what are residual values and how you find them
length of vertical line joing data point to regression line
= actual y value - pred. y value
what seasonal trend
data fluctuates according to the calendar
what cyclical trend
fluctuations repeat due to reasons other than the calendar
what irregular trend
no obvious pattern
what is an arithmetic sequence
the dif. between any two successive terms
whats the common dif, how do you find (arithmetic sequences)
d = tn+1 - tn
e.g.
t2 - t1, t3 - t2, etc
how to make predictions using arithmetic sequence rule
tn = t1 + (n-1)d
