Creating a relative frequency table for one categorical variable
About this video
A weather station recorded the type of precipitation on 50 days: 27 rain, 15 snow, 6 sleet and the rest hail. The video turns each count into a relative frequency by dividing by 50, giving 0.54, 0.30, 0.12 and 0.04, and works out that hail fell on 2 days.
You'll be able to
- calculate the relative frequency of a category by dividing its count by the total.
- complete a relative frequency table for one categorical variable.
- find a missing count using the total.
Key words
- relative frequency
- The fraction or proportion of the total that falls in a category: count divided by total.
- categorical variable
- A variable whose values are categories, like rain, snow, sleet or hail.
- distribution
- How the data are spread across the possible values or categories.
Transcript
- [Instructor] We're told that a mountain weather station recorded the type of precipitation on each of the 50 days it recorded any precipitation. The results were, and they tell us the results. Complete the relative frequency table showing the distribution of precipitation types.
All right. Like always, pause the video, have a go at it, and then we'll do it together. All right. So relative frequency. So we really just want to think about what proportion of the days were rain, were snow, were sleet, or hail? Well, rain was 27 out of 50 of the days.
So 27 out of 50. This is the same thing as 54 over 100, or 0.54. I can write that right over here. Then snow is 15 out of 50 days. This is the same thing as 30 out of 100 days, or 0.30. 0.30. Sleet is 6 out of the 50 days, which is equal to 12 out of 100, which is equal to 0.12.
0.12. And then last but not least, hail was the rest of the days. So how many days did we not count? So let's see. If we have 27 plus 15 plus 6, that's going to be 7 plus 5 is 12 plus 6 is 18. And then, let's see, this gets us to 4, or 48. So the rest of the days were actually two days.
Right over here, they could have just said that, but they're making us do a little bit of math. Two days. So this is 2 out of the 50 days, which is the same thing as 4 out of 100, which is the same thing as 4/100. 0.04. And we're done.
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