# Introduction to statistics

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The table below shows the results of a tryout of a 10 –item test in statistics done by BED students, ( see the complete question in the attachment below............

Introduction to statistics, MEASUREMENTS AND EVALUATION QUESTION ONE The table below shows the results of a tryout of a 10 –item test in statistics done by BECD students. Item Upper Number 27% Lower 27% Difficulty Discrimination Decision Justification of decision index index taken A-Rejected B-Retained C-Revised 1. 20 18 0.38 2. 19 12 0.31 3. 17 11 4. 10 20 5. 21 11 6. 9 2 7. 24 14 8. 19 13 9. 9 19 10. 22 15 a. Complete the table above (100 students tested) (9 marks) b. What do the numbers in column ‘Upper 27%’ and ‘Lower 27%’ mean? (5 marks) 1 c. How many items were Rejected, Retained or Revised? Give your justification in the table above (6 marks) QUESTION TWO (14 marks) Mr. Ibu of Baraka primary school was analyzing results of Mathematics of his candidates. He found a mean score of 62 marks. Later on during presentation, he realizes that he made an error by adding 2 candidates’ scores as 48 and 5 instead of 84 and 59 respectively. If the sum of the squares of the scores deviations from the correct mean was 1050 with a standard deviation of 5, find the correct mean of Mr. Ibu’s Mathematics class. (10 marks) 2

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