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Histograms: Finding the Frequency
Histograms: Finding the Frequency
We can work backwards from histograms to find the frequency of a given interval.
We can work backwards from a histogram to infer information and data.
Which is the correct formula for finding the frequency density?
Remember the formula for frequency density
When we have a histogram, or are already given the frequency density, we can rearrange this formula to give us the frequency.
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/CnvlM9R6RCmEYSpdVHpV.png)
By rearranging, we find this formula
This is useful because frequency is raw data which we can draw insight from if it is not initially provided.
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/Vwgbew1LRSHhlAWexAq7.png)
This table describes the histogram
We have the frequency densities already, so can apply our formula to find the frequency.
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/CDOAXOPHTbanJo2ATo9e.png)
At 0≤m<20, the frequency is 4
The frequency density is 0.2 and the class width is 20. Therefore 0.2×20=4. There must have been 4 fruits between the mass of 0 and 20 grams.
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/CDOAXOPHTbanJo2ATo9e.png)
What was the frequency at the interval 20≤m<30
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/CDOAXOPHTbanJo2ATo9e.png)
The frequency at 20≤m<30 is 12
The frequency density is 1.2, while the class width is 10. Therefore, 1.2×10=12
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/vaGddf0Q0uDrpt1Z3PG3.png)
What is the frequency at the interval 45≤m<60
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/vaGddf0Q0uDrpt1Z3PG3.png)
The frequency at 45≤m<60 is 9
The frequency density is 0.6, while the class width is 15. Therefore, 0.6×15=9
![](https://cdn.hejalbert.se/teen/blocks-images/en_GB/IYA94Y0tRGvQOWBc5mSu.png)