To find the mean of a frequency distribution with intervals, we first need to find the midpoint of each interval.
We do that by adding the limits of each interval and dividing by 2:
1
![(40+44)/(2)=42](https://img.qammunity.org/2023/formulas/mathematics/college/71hlglp90e9q91j3ijpknn43hy0maa3l5w.png)
2
![(45+49)/(2)=47](https://img.qammunity.org/2023/formulas/mathematics/college/zduhbgvcn0qv92tyhl1h74da2rm5d54tr1.png)
3
![(50+54)/(2)=52](https://img.qammunity.org/2023/formulas/mathematics/college/ut66w732d8c9jitv305ihszexu5qx7mieb.png)
4
![(55+59)/(2)=57](https://img.qammunity.org/2023/formulas/mathematics/college/xdeidtxepgdvwsyxamg3yjzql7lgnbbl9a.png)
5
![(60+64)/(2)=62](https://img.qammunity.org/2023/formulas/mathematics/college/3i2bp6k35o17q6yym8g22cezd2v6cvf9fr.png)
Now, we multiply these midpoints by the frequency of each interval and sum them:
![\begin{gathered} 3\cdot42+7\cdot47+11\cdot52+5\cdot57+2\cdot62 \\ 126+329+572+285+124=1436 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/33ddf5xojadb663vmorhg9neh90aqmkf6j.png)
Now, we divide this sum by the sum of the frequencies, and this will be the mean.
![m=(1436)/(3+7+11+5+2)=(1436)/(28)=51.3](https://img.qammunity.org/2023/formulas/mathematics/college/497azkxqwoqxi924b04o21o4rm84c6e4j9.png)
So, the mean calculated by using the frequency distribution is 51.3, which is lower than the actual mean of the data, 56.3.