statistics probability

The following table shows the time spent in reading a book by a group of standard six students from Permata Primary School. Time (in minutes) Number of students 30 - 39 25 40 - 49 16 50 - 59 12 60 - 69 7 70 -79 5 i) Construct a 'less than' ogive for the data above. ii) Estimate the median value using the ogive in (i). iii) Calculate the mean and the standard deviation for the data above. iv) Estimate the percentage of students who spent more than one hour to read a book using the ogive in (i). v) The mean and variance of time to read a book by a group of students from Primary School are 43.21 and 234.7 respectively. Determine which group of students is more consistent in the time spent reading a book