The median class for the given data is
Height (in cm) Less than 140 Less than 145 Less than 150Less than 155Less than 160Less than 165No. of girls41129404651
145-150
The given table can be written as:
Height (in cm) Less than 140 Less than 145 Less than 150Less than 155Less than 160Less than 165No. of girls41129404651
Height (in cm) Less than 140140−145145−150150−155155−160160−165Cumulative Frequency41129404651
n = 51
∴n2=512
= 25.5
Since there are a total of 51 observations, the median class is the one whose cumulative frequency is closest to and greater than 25.5. The cumulative frequency for the class '145 - 150' is 29 which is greater than 25.5. The median class is '140 - 145'. Thus, the class interval '145 - 150' is the required answer.