A first sample of 30 values has mean 20 and standard deviation 5.
A second sample of 20 values is combined with the first. The 50 values together have mean 22 and standard deviation 6.
Find the mean of the second sample.
Find the standard deviation of the second sample.
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.