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neurologyYou need to know

• In a tally chart, tallies are grouped in fives with the fifth mark crossing the previous four, and the frequency is the total number of tallies recorded for a category.
• In a pictogram, each symbol represents a fixed number of items defined by the key, and half symbols represent half the key value when needed.
• In a bar chart, categories are placed on the horizontal axis and frequency on the vertical axis; bars have equal width, equal spacing, and gaps between bars to show discrete categories.
• In a dual bar chart, two bars are drawn side by side for each category to compare data sets, and a clear legend (key) identifies each data set.
• In a line graph for time series, time is on the horizontal axis and the variable is on the vertical axis; plotted points are joined to show how the value changes over time.
• A timetable is a structured table of departure and arrival times; 24-hour time runs from 00:00 to 23:59 and is written without am/pm.
• The duration of a journey equals arrival time minus departure time, accounting for hour and day changes when calculating across midnight or multiple services.
• A scatter diagram plots paired bivariate data as points, with the explanatory variable on the horizontal axis and the response variable on the vertical axis.
• Positive correlation means that as x increases, y tends to increase; negative correlation means that as x increases, y tends to decrease; zero correlation shows no linear trend.
• Correlation does not imply causation; two variables can be correlated without either variable causing the other.
• A line of best fit on a scatter diagram is a straight line drawn by eye that follows the overall trend and leaves roughly equal numbers of points on each side.
• Interpolation estimates a value within the observed data range, while extrapolation estimates beyond the data range and is less reliable.
• In a pie chart, each sector’s angle is proportional to its frequency, calculated by `\text{angle} = \frac{\text{frequency}}{\text{total}} \times 360^\circ`; the full circle is 360°.
• In a conversion graph for a proportional relationship, the graph is a straight line through the origin and its gradient represents the conversion rate between the two units.
• A frequency tree shows totals and branch frequencies at each stage; the sum of branch frequencies at a node equals the parent total.
• In a stem-and-leaf diagram, the stem contains the leading digits and the leaves contain the final digits; the leaves are ordered and a key shows how to read a value.
• From a stem-and-leaf diagram (or raw data), `\text{mean} = \frac{\text{sum of values}}{\text{number of values}}`, the median is the middle value when ordered, the mode is the most frequent value, and the range is `\text{maximum} - \text{minimum}`.
• A frequency polygon represents a distribution by plotting frequency at each class midpoint and joining the points with straight lines; axes are labelled with the variable and frequency.
• For grouped data, the class midpoint is `\frac{\text{lower class limit} + \text{upper class limit}}{2}` and is used as the plotting position in a frequency polygon.
• Clear titles, labelled axes with units, consistent linear scales, and accurate keys are essential features for valid construction and interpretation of statistical diagrams.

• Construct a tally and frequency table from raw data, grouping tallies in fives and totalling frequencies accurately.
• Draw a pictogram using a clear key, using whole or half symbols as needed and aligning symbols neatly in rows or columns.
• Draw a bar chart or dual bar chart by choosing an appropriate linear scale, labelling axes, keeping bar widths equal, leaving gaps between categories, and adding a legend for dual bars.
• Read and use a timetable to select feasible journeys, find the next available departure, and calculate journey durations including changes between services.
• Plot and interpret line-based graphs: for time series, place time on the horizontal axis, plot points accurately and join them to show change; for frequency polygons, plot class midpoints against frequency and join with straight lines.
• Plot a scatter diagram from paired data, identify the type and strength of correlation (positive, negative or none), and describe the relationship succinctly.
• Draw a straight line of best fit by eye on a scatter diagram and use it to estimate missing values by interpolation; state why estimates made by extrapolation are less reliable.
• Draw and interpret a pie chart by calculating sector angles with `\text{angle} = \frac{\text{frequency}}{\text{total}} \times 360^\circ`, measuring with a protractor, and adding clear labels and a key.
• Build and use a frequency tree by filling totals and branch frequencies so that subtotals add correctly, then answer questions about combined and conditional counts.
• Draw a stem-and-leaf diagram with ordered leaves and a clear key, then find the mean, median, mode and range from the diagram.