The Chief Examiner reported that although this question was popular among the candidates, majority of them could not obtain the value of x which showed poor knowledge of the concept of probability. Others were not able to handle the fractions involved. Candidates were expected to obtain the total frequency as 2 + 5 + x + 11 + 9 + 10 = 37 + x. Since the probability of a 3 is 0.26, then  = 0.26. By cross multiplying and bringing like terms together, we obtain x = 13.
333
Thus, the total frequency becomes 50. The median = average of the 25th and 26th score = 4.    From the table,

Score (x)	Frequency f	fx	fx2
1	2	2	2
2	5	10	20
3	13	39	117
4	11	44	176
5	9	45	225
6	10	60	360
Total	Σf = 50	Σfx = 200	Σfx2 = 900

                                                    

 

 

Standard deviation =  = 1.41