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neurologyYou need to know

• The mode is the value or category with the highest frequency in a data set.
• The range is the largest value minus the smallest value, and it measures the spread of a data set.
• The median is the middle value when data values are placed in order from smallest to largest.
• In a frequency table, the total frequency is the total number of data values and is found by adding all the frequencies.
• In a frequency table, the modal value or modal class is the value or class interval with the highest frequency.
• In a frequency table for discrete data, the median position is found using `\frac{n+1}{2}`, where `n` is the total frequency.
• The mean from a frequency table is calculated using `\frac{\text{total of }fx}{\text{total frequency}}`, where `f` is frequency and `x` is the data value.
• A cumulative frequency is a running total of the frequencies up to and including each value or class interval.
• Grouped data uses class intervals, so exact individual data values are not known.
• For grouped data, the median class is the class interval that contains the `\frac{n}{2}`th value, where `n` is the total frequency.
• For grouped data, the mean is estimated by using the midpoint of each class interval as a representative value.
• The midpoint of a class interval is calculated using `\frac{\text{lower class boundary}+\text{upper class boundary}}{2}`.
• The estimated mean from grouped data is calculated using `\frac{\text{total of }fm}{\text{total frequency}}`, where `f` is frequency and `m` is class midpoint.
• Linear interpolation estimates a value within a class interval by assuming the data are evenly spread across that interval.
• The lower quartile is the value one quarter of the way through an ordered data set, and the upper quartile is the value three quarters of the way through an ordered data set.
• The interquartile range is calculated using `\text{upper quartile} - \text{lower quartile}`, and it measures the spread of the middle 50% of the data.
• Averages describe typical values, while measures of spread such as the range and interquartile range describe how varied the data are.
• The median and interquartile range are less affected by extreme values than the mean and range.

• Find the mode from a frequency table by identifying the value or class interval with the greatest frequency.
• Calculate the range from a frequency table by subtracting the smallest data value with non-zero frequency from the largest data value with non-zero frequency.
• Find the median from a frequency table by calculating the median position, using cumulative frequencies, and selecting the value at that position.
• Calculate the mean from a frequency table by multiplying each value by its frequency, adding the products, and dividing by the total frequency.
• Identify the median class in grouped data by using cumulative frequency to locate the class interval containing the middle value.
• Estimate the mean from grouped data by finding class midpoints, multiplying each midpoint by its frequency, and dividing the total by the total frequency.
• Use linear interpolation to estimate the median from grouped data by locating the median class and scaling the distance through that class according to cumulative frequency.
• Find the lower quartile, upper quartile and interquartile range from an ordered data set using appropriate quartile positions and subtracting the lower quartile from the upper quartile.
• Compare two distributions by referring to a suitable average for typical value and a suitable measure of spread, using values from the data to support the comparison.