A-Level Maths Specification

OCR A H240

Section 2.02: Data presentation and interpretation

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#2.02a

Be able to interpret tables and diagrams for single-variable data.

e.g. vertical line charts, dot plots, bar charts, stem-and-leaf diagrams, box-and-whisker plots, cumulative frequency diagrams and histograms (with either equal or unequal class intervals). Includes non-standard representations.

Histograms and frequency polygons Box and whisker plots Cumulative frequency diagrams

#2.02b

Understand that area in a histogram represents frequency.

Includes the link between histograms and probability distributions.

Includes understanding, in context, the advantages and disadvantages of different statistical diagrams.

Histograms and frequency polygons

#2.02c

Be able to interpret scatter diagrams and regression lines for bivariate data, including recognition of scatter diagrams which include distinct sections of the population.

Learners may be asked to add to diagrams in order to interpret data, but not to draw complete scatter diagrams.

[Calculation of equations of regression lines is excluded.]

Scatter graphs Regression lines

#2.02d

Be able to understand informal interpretation of correlation.

Correlation

#2.02e

Be able to understand that correlation does not imply causation.

Correlation

#2.02f

Be able to calculate and interpret measures of central tendency and variation, including mean, median, mode, percentile, quartile, inter-quartile range, standard deviation and variance.

Includes understanding that standard deviation is the root mean square deviation from the mean.

Includes using the mean and standard deviation to compare distributions.

Mean, mode and median Variance and standard deviation Range and interquartile range Linear interpolation

#2.02g

Be able to calculate mean and standard deviation from a list of data, from summary statistics or from a frequency distribution, using calculator statistical functions.

Includes understanding that, in the case of a grouped frequency distribution, the calculated mean and standard deviation are estimates.

Learners should understand and be able to use the following formulae for standard deviation:

\(\sqrt{\dfrac{\sum{(x-\bar{x})^2}}{n}} = \sqrt{\dfrac{\sum{x^2}}{n} - \bar{x}^2} \),

\(\sqrt{\dfrac{\sum{f(x-\bar{x})^2}}{\sum{f}}} = \sqrt{\dfrac{\sum{fx^2}}{\sum{f}} - \bar{x}^2} \).

[Formal estimation of population variance from a sample is excluded. Learners should be aware that there are different naming and symbol conventions for these measures and what the symbols on their calculator represent.]

Variance and standard deviation Coding data

#2.02h

Recognise and be able to interpret possible outliers in data sets and statistical diagrams.

Outliers and cleaning data

#2.02i

Be able to select or critique data presentation techniques in the context of a statistical problem.

Select or critique data presentation techniques

#2.02j

Be able to clean data, including dealing with missing data, errors and outliers.

Learners should be familiar with definitions of outliers:
1. more than \(1.5 ×\) (interquartile range) from the nearer quartile,
2. more than \(2 ×\) (standard deviation) away from the mean.

Outliers and cleaning data