4. The table summarises the percentage marks obtained by 200 students sitting an examination. (a)Find the mean and standard deviation of the marks. State the assumption that you make. (b)Use

the method of interpolation to determine the median for the data. (c) Two further sets of data have the following properties: \text { Set 1: } \bar{x}_{1}=16, \sigma_{1}=3, n=24 \text { Set } 2: \bar{x}_{2}=13, \sigma_{2}=5, n=20 (i)find the combined mean for the data find the scaling formula that maps Set 2 onto Set 1.