Frequency Tables and Analysis
Frequency tables might look boring, but they're actually data goldmines that help you find patterns and answer exam questions worth serious marks. The cumulative frequency column shows running totals - just add each frequency to the previous total.
To find the estimated mean, use the formula: Sum of (midpoint × frequency) ÷ total frequency. Pick the midpoint of each class interval, multiply by its frequency, add them all up, then divide by the total number of values.
The modal class is simply the group with the highest frequency - easy marks if you spot it quickly! For the median, find the middle position (total ÷ 2) and see which class it falls into using your cumulative frequency.
Exam Smart: Cumulative frequency graphs use smooth curves, not straight lines. Connect your plotted points with a flowing curve to find the median accurately.