Question

Find the mean of the following data using the direct method:

Hint:

The direct method is best when class intervals and frequencies are simple. Always verify midpoints and products.

Answer 1

Step 1: Calculate midpoints (x): \[ \text{Class midpoints: } 5, 15, 25, 35, 45 \] Step 2: Create frequency × midpoint table: 

Step 3: Apply the direct mean formula: \[ \text{Mean} = \frac{\sum fx}{\sum f} = \frac{1060}{40} = \boxed{26.5} \]