The times, t t\,t seconds, taken by 30 cars to accelerate from rest to a fixed speed are coded using
y=t−ab\displaystyle y = \frac{t - a}{b}y=bt−a
where a a\,a and b b\,b are constants and b>0b > 0b>0.
The 30 coded values have mean 4 and standard deviation 2.5. The 30 original times have mean 74 seconds and standard deviation 12.5 seconds.
Find the value of bbb.
Find the value of aaa.
The median of the coded values is 3.6. Find the median of the original times.
244 exam-style questions on AQA A Level Maths 2.2 L: Data presentation and interpretation, covering 2.2.1 Single-variable data diagrams, 2.2.2 Scatter diagrams and correlation, 2.2.3 Central tendency, variation and standard deviation, 2.2.4 Outliers and cleaning data, and 2.2 L: Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.