This activity, together with the following activities Investigating heights, Investigating pets, shoe sizes and travel times and Comparing groups, can used to give context to mean, median, mode and range. Students must understand that the mean and median only applies to numerical data. They will see that they are presented with a situation in which the median is middle of two categories and therefore cannot be found. To address this, provide an example using categorical data with an even number of data and ask students to find the median. This will help students see how these statistics allow us to make sense of the data by presenting it in a more meaningful way and how we can use these statistics to hypothesise.Ī common misconception is that students try to find the mean or median of categorical data. You may also want to collect data from another class or from an older cohort of students and then compare the statistics calculated. Whilst there is no need to introduce outliers formally at this stage, if there is a student or person in the room who is considerably taller or shorter than most, it may be worth students investigating what impact this value will have on the statistics calculated.Īsk students to find the mean, median, mode and range and discuss what these values tell us about the heights of everyone in the classroom. For example, you may want to see what the average height (rounded to the nearest centimetre) and what range of heights there are in the classroom. When introducing these concepts begin with smaller data sets that are easy to work with and data that is contextual so that students see the purpose of calculating these statistics. While it is the simplest measure of spread, it is not always accurate or reliable as it only uses two values and therefore does not give an indication of the spread of the rest of the data. This means the data is more clustered around the mean value. The smaller the range, the less varied the data is. This is the difference between the greatest value in the data set and the smallest value. The only measure of spread that needs to be considered at this level is range. For example, when the most frequent value is far away from the rest of the data in the set.Ī measure of spread describes how varied or 'spread out' the data is in comparison to the mean. This is not always a good measure of the centre. Mode – this is the most frequently occurring value in the data set.Median – is the middle value of the data which must first be arranged in ascending order.While this is the most common measure, it is not always the most effective. To calculate the mean, add all the data values and divide by the total number of data. Mean - students may already have a basic understanding of mean in terms of the average value.Generally, it is around this value that most of the data will lie. ![]() ![]() ![]() Students should understand that a measure of centre attempts to describe the data set by identifying the central position of the data set. They will interpret these statistics and understand how these can help make sense of the data. At this level, students will calculate measures of centre mean, median and mode, and measures of spread, namely the range of data sets.
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