ch 4 correlation Flashcards
What are scatter graphs?
They are a way of representing two sets of data (bivariate)
What is positive correlation?
As one variable increases so does the other.
What is negative correlation?
As one variable increases the other decreases.
What is no correlation?
No pattern in data set.
What is correlation?
Correlation describes the nature of the linear relationship of two variables.
What is linear regression?
Creating a line of best fit for data.
What is a method of linear regression and how does it work?
- Least squares regression line.
- Does this by minimising the squared area between points and the line.
For a question with linear regression line g= 7.23 + 1.82w
how would you interpret gradient and y intercept?
X axis = daily mean windspeed
Y axis = daily maximum gust
What is important about this?
gradient= a change in 1 of the daily mean windspeed create a 1.82 change in daily maximum gust.
ALWAYS CHECK UNITS OF QUESTION.
How could you justify the use of a linear regression line ?
As the two variables have a linear relationship a linear regression line is suitable.
What is important to remember when making predictions using a linear regression line?
What two situations can this cause?
-The prediction will always be more accurate if the values are within the range of values.
(Interpolation when it is in the range of values).
(Extrapolation when it is outside the range of values).
A nurse wants to estimate the gestation period of a baby born with a head circumference of 31.6cm.
describe the accuracy of this?
When is estimation always accurate?
- It is less accurate as the dependent variable is being use to dictate the independent variable.
- When the independent variable is being used to describe the dependent variable.
