CHAPTER 4 Flashcards
1
Q
when do two variable have an association?
A
- when there is a relationship between them
2
Q
where should you plot the explanatory (independent) variable when drawing a scatter diagram?
A
- x axis
3
Q
what is correlation?
A
- association between two variables that show increasing or decreasing trend
4
Q
what is positive correlation?
A
- one variable increases when the other increases
5
Q
what is negative correlation?
A
- when one variable decreases as the other increases
6
Q
when is the correlation linear?
A
- when the points lie on or are near a straight line
7
Q
what is a causal relationship?
A
- when a change in one variable directly causes a change in another variable, there is a causal relationship between them
- correlation does not necessarily imply a causal relationship
8
Q
how to get a good fit when drawing a line of best fit:
A
- draw line through mean point
- sometimes written as (x, y)
both with lines on top
9
Q
what is interpolation?
A
- using a line of best fit to estimate values within the data range
- usually reliable
10
Q
what is extrapolation?
A
- using a line of best fit to estimate values outside the data range
- less reliable as they are further away from the range of data
11
Q
equation of a line of best fit:
A
- y= ax + b
- a= gradient
- b= y intercept
12
Q
what is the other name for the line of best fit?
A
- regression line
13
Q
what does the gradient of a line of best fit represent?
A
- rate of increase of the response variable in relation to the explanatory variable
14
Q
what does the y- intercept of a line of best fit represent?
A
- value of response variable when the explanatory variable is 0
15
Q
what does spearman’s rank correlation coefficient measure?
A
- strength of correlation between two sets of data
