A road-safety researcher believes that, for cars of a given model, there is a negative correlation between the age of the car in years and its fuel economy in miles per gallon.

She collects data from a random sample of 30 cars of this model. The product moment correlation coefficient between age and fuel economy for this sample is -0.38.

For these data, the $p$ -value for a one-tailed test of the population correlation coefficient is 0.019.

Carry out a hypothesis test at the 5% significance level to determine whether the sample supports the researcher's belief.

The researcher concludes that a car becoming older causes its fuel economy to fall. Explain why her data alone do not justify this conclusion.

A road-safety researcher believes that, for cars of a given model, there is a negative correlation between the age of the car in years and its fuel economy in miles per gallon.

She collects data from a random sample of 30 cars of this model. The product moment correlation coefficient between age and fuel economy for this sample is -0.38.

For these data, the $p$ -value for a one-tailed test of the population correlation coefficient is 0.019.

Carry out a hypothesis test at the 5% significance level to determine whether the sample supports the researcher's belief.

The researcher concludes that a car becoming older causes its fuel economy to fall. Explain why her data alone do not justify this conclusion.

2.2.2 Scatter diagrams and correlation

Question 28

Markscheme

2.2.2 Scatter diagrams and correlation

Question 28

Markscheme

2.2.2 Scatter diagrams and correlation

Question 28

2.2.2 Scatter diagrams and correlation Questions

2.2.2 Scatter diagrams and correlation

Question 28

2.2.2 Scatter diagrams and correlation Questions