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neurologyYou need to know

• The mode is the value or category that occurs most often in a data set.
• A data set can have no mode, one mode, or more than one mode if values are equally most frequent.
• The median is the middle value when all data values are written in order from smallest to largest.
• If a data set has an even number of values, the median is the mean of the two middle values after the data is ordered.
• The mean is the total of all data values divided by the number of data values.
• The range is the largest value minus the smallest value in a data set.
• A frequency table shows each value or category and the number of times it occurs.
• In a frequency table, the total frequency is the total number of data values.
• In a frequency table for discrete data, the mode is the value with the greatest frequency.
• In a frequency table for discrete data, the range is the largest value with a non-zero frequency minus the smallest value with a non-zero frequency.
• In a frequency table, the median is found by locating the middle position in the ordered data using the frequencies.
• For `n` data values, the median position is the `\frac{n+1}{2}`th value when `n` is odd.
• For `n` data values, when `n` is even, the median is the mean of the `\frac{n}{2}`th and `\frac{n}{2}+1`th values.
• To calculate the mean from a frequency table, multiply each value by its frequency, add these products, and divide by the total frequency.
• Grouped data is data placed into class intervals, such as 0–10 or 10–20, rather than listed as exact values.
• For grouped data, the exact median and exact mean cannot usually be found because the original values inside each class interval are not known.
• The median class is the class interval that contains the middle value of a grouped frequency table.
• The estimated mean from grouped data is found using the midpoint of each class interval as an estimate for all values in that class.
• The midpoint of a class interval is found by adding the lower and upper class boundaries and dividing by 2.

• Order a raw data set from smallest to largest before finding the median, mode, range, or mean.
• Find the mode from a raw data set or frequency table by identifying the value or category with the highest frequency.
• Calculate the range by subtracting the smallest data value from the largest data value, ignoring values with zero frequency in a frequency table.
• Find the median from a raw data set by ordering the values and selecting the middle value, or averaging the two middle values when there is an even number of values.
• Find the median from a frequency table by using the total frequency to identify the middle position and then using cumulative counting to locate the corresponding value.
• Calculate the mean from a raw data set by adding all values and dividing by the number of values.
• Calculate the mean from a frequency table by completing a value multiplied by frequency column, adding the products, and dividing by the total frequency.
• Identify the median class in grouped data by finding the middle position from the total frequency and using cumulative frequencies to locate the class interval containing it.
• Estimate the mean from grouped data by finding each class midpoint, multiplying each midpoint by its frequency, adding these products, and dividing by the total frequency.