Two groups have regression lines y=5+1.8xy=5+1.8xy=5+1.8x and y=23+0.6xy=23+0.6xy=23+0.6x. The observed xxx-range for both groups is 4≤x≤124\leq x\leq124≤x≤12.
Find where the lines intersect.
Determine which line gives the larger prediction throughout the observed range.
Explain why the intersection should not be interpreted as an observed equality.
121 exam-style questions on OCR A Level Maths 2.2 Data Presentation and Interpretation, covering 2.2.1 Tables and diagrams for single variable data, 2.2.2 Area in a histogram, 2.2.3 Scatter diagrams and regression lines, 2.2.4 Informal interpretation of correlation, 2.2.5 Correlation and causation, 2.2.6 Measures of average and spread, 2.2.7 Calculations of mean and standard deviation, 2.2.8 Outliers, 2.2.9 Selecting or critiquing data presentation, and 2.2.10 Cleaning data. Each one has a worked solution and a mark scheme showing where the marks go.