Brainlag Plus
Brainlag PlusStatistics and probability problems
Combined means and targets, grouped data, probabilities in terms of x, picks without replacement, Venn diagrams, histograms and expected profit.
Think in totals
A mean hides a total. Turn it back into one.
- 12 pupils with a mean of 60 have 12 × 60 = 720 marks altogether
- 8 more with a mean of 45 add 8 × 45 = 360
- together: 1080 ÷ 20 = 54
- for a mean of 55 with one more pupil, the total must be 55 × 21 = 1155, so they need 1155 − 1080 = 75
The rest of this lesson and its 11 practice questions are in Plus.
Screen 1 of 3, free to read.
- 11 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards