See what we can offer to your school
"SimpleStudy just makes sense...”
Get the best plan for your school
10 cards from this deck
SD = sqrt[(∑fx²/∑f) - (∑fx/∑f)²] for grouped data.
Using midpoints to represent all values gives an estimate, not exact.
Midpoint, f×Mid, and f×Mid² columns.
Because midpoints approximate all data values within intervals.
To three significant figures unless directed otherwise.
Seconds, matching the original data units.
SD ≈ 23.4 s
f×mid = 330, f×mid² = 9900
Midpoints represent class values, not exact data
SD = √(104800/40 - (1820/40)^2) = 23.4 s
Select your subjects, and get access to A+ resources today.