In this lesson:
You will be able to:
Ten-second check: write as a decimal and a percent. ;
Answer formats:
A bag has 4 red, 3 blue, and 5 green marbles. One is drawn at random.
Recall: grand total 200; row totals 80 and 120.
Chosen from all 200:
Reverse: a student is chosen at random from 200, and . How many are in Grade 9?
Count = probability × total.
A point is chosen at random in the rectangle.
Die:
Table:
Faster than adding .
Cannot overlap? :
From the survey table (200 students), :
The 35 Grade 9 science students are counted twice, so subtract them once. Without it: , too large.
People count: Grade 9 (80) + Grade 10 science (70) = 150 ✓
Range: Grade 10 or science without subtracting: . Correct: .
is below 1 and slips through: count people.
"And" is one cell:
From all 200 students, one is chosen. What is ?
A) B) C) D)
Answer: C. . Choice A uses the row total, 80.
Answer: . Enter or .
Either form is accepted; do not type a percent sign.
From all 200 students, one is chosen. ?
The entry field takes 5 characters: does not fit. Enter or .
Wrong denominator: ask what group you select from
Overlap forgotten: answer too large
Next lesson: Conditional Probability
You will learn:
Conditional probability uses the same tables — just a different denominator.