7.SP.5: Probability as a Number from 0 to 1
Also written as 7.SP.C.5 and CCSS.MATH.CONTENT.7.SP.C.5 · Cluster: Investigate chance processes and develop, use, and evaluate probability models.
The Official Wording
Understand that the probability of a chance event is a number between 0 and 1 that expresses the likelihood of the event occurring. Larger numbers indicate greater likelihood. A probability near 0 indicates an unlikely event, a probability around 1/2 indicates an event that is neither unlikely nor likely, and a probability near 1 indicates a likely event.
Common Core State Standards, Grade 7, Statistics & Probability · Read it at the source · Checked October 14, 2026
What 7.SP.5 Means in Plain English
Seventh graders learn that a probability is a number from 0 to 1, and read where it falls. In a bag of 20 marbles with 1 gold, drawing gold is 1/20 = 0.05, unlikely; drawing blue, 10 of the 20, is 0.5, as likely as not.
0 means impossible and 1 means certain, so an answer like 1.2 or 20 signals a mistake. 7.SP.6 and 7.SP.7 then find probabilities from data and models, and high school describes events as subsets of a sample space (HSS-CP.1).
7.SP.5 I Can Statements
- I can explain why every probability is between 0 and 1.
- I can place an event on a likelihood line from 0 to 1.
- I can describe a probability as unlikely, as likely as not, or likely.
7.SP.5 Worked Example
One bag of marbles, five events, and a number line from 0 to 1 that turns each probability into words.
A bag holds 20 marbles: 1 gold, 9 green and 10 blue. One marble is drawn without looking. Find the probability of drawing gold, blue, not gold, purple, and any marble, and describe how likely each is.
- A probability compares the outcomes you want with all the outcomes. There are 20 marbles and 1 is gold.P(gold) = 1/20 = 0.05
- Blue is 10 of the 20 marbles, exactly half the bag.P(blue) = 10/20 = 1/2 = 0.5
- Not gold means any of the other 19 marbles.P(not gold) = 19/20 = 0.95
- The ends of the line: there are no purple marbles, and every draw is a marble.P(purple) = 0/20 = 0; P(any marble) = 20/20 = 1
- Place all five on a number line from 0 to 1 and read the words off it.0 impossible, 0.05 unlikely, 0.5 as likely as not, 0.95 likely, 1 certain
Check it: Gold and not gold cover every possible draw, so their probabilities must add to 1: 0.05 + 0.95 = 1. Every answer also sits between 0 and 1, as a probability must.
Common Mistakes with 7.SP.5
Writing the fraction upside down
P(gold) = 20/1 = 20
Try this: Put the outcomes you want on top and all outcomes below; any answer greater than 1 means the fraction is flipped.
Treating unlikely as impossible
P(gold) is 0.05, so nobody will ever draw gold
Try this: Say it as a count: 0.05 means about 1 draw in 20, so in 100 draws with replacement gold shows up about 5 times.
Judging likelihood by count, not share
Bag A has 3 red of 4 marbles and bag B has 10 red of 30, so bag B is likelier because 10 is more than 3
Try this: Compare fractions of each bag, not counts: 3/4 = 0.75 is likely, while 10/30 is about 0.33, less likely than not.
Where 7.SP.5 Fits
Practice 7.SP.5
Quick Check
- A spinner has 8 equal sections, 6 of them red. What is P(red), and how likely is it?
- Is a probability of 0.48 unlikely, about as likely as not, or likely?
- A student says the probability of rain tomorrow is 1.3. What is wrong?