Edexcel GCSE Statistics Scatter diagrams and correlation overview quiz quiz

Positive

Negative

Zero

Spurious

Buying an ice cream directly causes people to go swimming

Going for a swim directly causes people to go and buy ice cream

Both are affected by a third factor, hot weather

The correlation between them must simply be a calculation error

The origin

The highest data point

The median point

The double mean point

The value of $y$ when $x = 0$ (the intercept)

The gradient of the regression line itself

The mean of the $x$ values in the data set

The value of the correlation coefficient for the data

$0.4$

$0.6$

$0.8$

$1.0$

Perfect agreement between the rankings

No relationship between the rankings

Complete disagreement (opposite rankings)

A calculation error, as it cannot be negative

Calculate it from the data

Use it to draw the line of best fit

Convert it to Spearman's rank

Only interpret a given value

Extrapolation

Interpolation

Correlation

Standardising

The relationship between the two variables is perfectly linear

The relationship is positive but non-linear

There is no relationship between the two variables at all

One of the two values must have been calculated wrongly

The value of $y$ at the point where $x = 0$ on the line

The strength of the correlation between the two variables

The change in $y$ for each unit increase in $x$

The mean of all of the data values together

Direct causation

Perfect linear correlation

Linear interpolation

Spurious correlation

Rank both consistently (for example highest = 1 for both)

Rank each of the two variables using a different convention from the other

Only rank one of the two variables and leave the other one unranked

Add the two sets of values together first before you rank any of them