# Day 94: So What is Confidence?

Today we finished the Jelly Blubber activity and looked at our results…had 7 kids gone yesterday for an LA field trip to see a play, so the data is a slightly sparse.  I revealed the true average length of the population of 100 Jelly Blubbers to be 19.4 mm and drew the red line down the chart to show its location.

We then counted the intervals that actually captured the true mean, filling in the dot.  Any confidence intervals that missed the true mean, I redrew in red and also put an x in the dot.

Using the proportion of CI that captured the true mean, we developed the concept of the confidence level. We then talked about how to interpret an individual confidence interval and practice writing the interpretations.  I like to use a lighthouse analogy: either the lighthouse sees or doesn’t see a ship that is within its range…and the range of the light is like the confidence interval. We followed up the conversation with a discussion about the mechanics of calculating a confidence interval.  Tomorrow I’ll have an opener problem to see if they really did get it!  How do you check to see if students “get it” and “retain it?”