For a random sample of 50 employees, coded journey times x x\,x have ∑fx=815\sum fx=815∑fx=815 and ∑fx2=16475\sum fx^2=16475∑fx2=16475. The coding is x=t−202\displaystyle x=\frac{t-20}{2}x=2t−20, where t t\,t is the actual time in minutes. Linear interpolation gives a coded median of 13.9.
Estimate the sample standard deviation of xxx.
Find the median and sample standard deviation of ttt.
121 exam-style questions on OCR (MEI) A Level Maths 2.2 Data Presentation and Interpretation, covering 2.2.1 Types of data and standard diagrams, 2.2.2 Area in a histogram is proportional to frequency, 2.2.3 Cumulative frequency diagram, 2.2.4 Describe frequency distributions, 2.2.5 Samples and theoretical distributions, 2.2.6 Interpret a scatter diagram, 2.2.7 Distinct sections and outliers in scatter diagrams, 2.2.8 Correlation and causation, 2.2.9 Select or critique data presentation techniques, 2.2.10 Measures of central tendency, 2.2.11 Simple measures of spread, 2.2.12 Variance and standard deviation, 2.2.13 Outliers, 2.2.14 Cleaning data, and 2.2 Data Presentation and Interpretation. Each one has a worked solution and a mark scheme showing where the marks go.