chapter 4 Flashcards
(26 cards)
when is it best to use scatter diagrams?
when it is bivariate data
what do scatter diagrams show?
whether 2 sets of data are associated
what is the variable that you change?
the explanatory (independent) variable
what is the other variable called?
the response (dependant) variable
when drawing a scatter diagram where does the explanatory variable go?
on the horizontal (x) axis
what is correlation?
an association between 2 variables that shows an increasing or decreasing trend
if the points are very scattered about a straight line, what type of correlation is this?
weak linear correlation
if the points formed make a curved line, what type of correlation is this?
non- linear correlation
when is a causal relationship formed?
when a change in one variable directly causes a change in another variable, there is a causal relationship between them
when do we draw a line of best fit?
if the scatter diagram shows linear correlation
where should the line of best fit go through?
the mean point
what is interpolation?
using a line of best fit to estimate data values from within the range of data
what is extrapolation?
using a line of best fit to estimate data values from outside the range of data
when are values estimated by extrapolation less reliable?
when they are further away from the line of best fit
what is the line of best fit also known as?
the regression line
what does the gradient (a) show?
the rate of increase of the response variable in relation to the explanatory variable
what does the y intercept (b) show?
the value of the response variable when the explanatory variable is 0
what does Spearman’s rank correlation coefficient show?
measures the strength of the correlation between 2 sets of data
if r is close to 1…
strong positive correlation
if r is 0…
no correlation
if r is close to -1…
there is strong negative correlation
what do you need to do first to calculate Spearman’s rank?
need to rank the data in each set
what does Pearson’s product test for?
linear correlation
what does Pearson’s product measure?
the strength of linear correlation between 2 sets of data
