Sarah believes there is a positive correlation between the amount of time spent practicing the piano and the score achieved in a music exam.
She calculates the product moment correlation coefficient between these two variables for a random sample of 20 students and obtains r=0.391r = 0.391r=0.391.
Carry out a suitable test to investigate Sarah's belief at a 5% level of significance.
State clearly
178 exam-style questions on WJEC A Level Maths 4.3.1 Statistical hypothesis testing (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.