For 50 coded journey times, xxx, the summary values are ∑x=815\sum x=815∑x=815 and ∑x2=16475\sum x^2=16475∑x2=16475. The actual time, t t\,t minutes, is related to x x\,x by t=2x+20t=2x+20t=2x+20.
Calculate the mean and standard deviation of xxx.
Hence calculate the mean and standard deviation of ttt.
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.