<h3>Organising data</h3><p>A <strong>frequency distribution table</strong> records how often each value or class of values occurs. It is the first step in making large data sets manageable.</p><h3>Measures of central tendency</h3><ul><li><strong>Mean:</strong> add all the values and divide by the number of values.</li><li><strong>Median:</strong> the middle value when the data is arranged in order.</li><li><strong>Mode:</strong> the value that appears most often.</li></ul><h3>Graphs</h3><p>A <strong>histogram</strong> uses bars whose areas show frequency, with no gaps between bars. A <strong>frequency polygon</strong> joins the midpoints of the tops of those bars with straight lines.</p><div class="callout"><strong>Kenyan context:</strong> A Grade 9 class scored 60, 70, 70, 80 and 90 in a maths CAT. The mean is <code>(60 + 70 + 70 + 80 + 90) ÷ 5 = 74</code>. Arranged in order, the median (middle) is 70, and the mode (most common) is also 70. A teacher can plot these marks as a histogram to see how the class performed.</div>