Outliers and cleaning dataEdexcel A-Level Maths: Mind map

Exam questions on Outliers and cleaning data

1. The numbers of text messages sent in one day by 40 students have minimum 3, lower quartile 14, upper quartile 22 and maximum 50. A value is an outlier if it is more than $1.5\times$IQR above the upper quartile or below the lower quartile.
   The maximum value of 50 was recorded in error and should have been 15. State what should be done with this value and find the effect on the mean.2 marks
2. The masses of 200 loaves from a bakery have mean 805 g and standard deviation 6 g. A loaf is classed as an outlier if its mass is more than 3 standard deviations from the mean.
   A loaf of mass 842 g is an outlier because the scale was faulty. Find the mean mass of the other 199 loaves.2 marks
3. A student measures the heights, in cm, of 8 plants. The values entered in a spreadsheet are 12.5, 13.1, 12.8, 128, 13.4, 12.9 and 13.0, and the cell for the eighth plant was left blank.
   Identify the likely error in the data, explain how you would deal with it, and calculate the mean height of the plants measured, after dealing with it.3 marks