Curriculum Portal

neurologyYou need to know

• A scatter graph plots paired data values as points, with the independent variable on the horizontal axis and the dependent variable on the vertical axis.
• A line of best fit is a straight line that shows the general trend of points on a scatter graph and usually has about as many points above the line as below it.
• Correlation describes the direction of association in a scatter graph: positive correlation rises left to right, negative correlation falls left to right, and no correlation shows no clear pattern.
• Correlation does not prove causation, because an association between two variables does not necessarily mean one causes the other.
• An outlier is a point that is far from the general pattern of the data and can affect a line of best fit and predictions.
• Interpolation means making a prediction within the range of the data shown, which is usually more reliable than extrapolation.
• Extrapolation means making a prediction outside the range of the data shown, which is less reliable because the pattern may not continue.
• A conversion graph shows the relationship between two measurement units, such as miles and kilometres, by plotting equivalent pairs of values.
• If one unit converts to another using a constant rate, the conversion graph is a straight line through the origin because 0 converts to 0.
• On a conversion graph, the gradient represents the conversion rate, which is how much the vertical-axis unit changes for each 1 unit on the horizontal axis.
• A stem-and-leaf diagram organises numerical data by splitting each value into a stem, consisting of the leading digit or digits, and a leaf, consisting of the final digit.
• In a stem-and-leaf diagram, leaves are written in ascending order for each stem so the data can be read quickly.
• A key in a stem-and-leaf diagram explains what the stems and leaves represent, for example, `3 | 7` means 37.
• The median is the middle value when the data is in order, or the mean of the two middle values if there is an even number of values.
• The mode is the most frequent value in a data set.
• The mean is found by adding all the data values and dividing by the number of values, i.e. `\text{mean}=\frac{\text{sum of values}}{\text{number of values}}`.
• The range is a simple measure of spread found by subtracting the smallest value from the largest value.

• Plot paired data accurately on a scatter graph by choosing sensible equal scales, labelling axes with variable names and units, and plotting each point in the correct position.
• Draw a line of best fit using a ruler so it follows the trend and has a balanced spread of points above and below, without forcing the line through every point.
• Describe correlation from a scatter graph by stating the direction (positive, negative, or none) and commenting on strength (strong or weak) based on how tightly the points cluster.
• Make a prediction from a line of best fit by selecting a given value on one axis, moving to the line, then reading across to the other axis and quoting an estimated value to a sensible precision.
• Judge the reliability of a prediction by stating whether it is interpolation or extrapolation and by commenting on how scattered the points are and whether there are outliers.
• Construct a conversion graph by plotting known equivalent pairs, drawing the straight line trend (through the origin for constant-rate conversions), and using it to convert values by reading across between axes.
• Interpret a conversion graph by explaining what the axes represent and using the graph to estimate conversions, including reading intermediate values accurately from the scale.
• Draw a stem-and-leaf diagram from a list of numbers by choosing appropriate stems, writing leaves in ascending order, and including a clear key.
• Calculate basic averages from a stem-and-leaf diagram by reading off the ordered data to find the median and mode, and by listing all values to find the mean using `\text{mean}=\frac{\text{sum}}{n}`.