Home Class 9 Worksheets Statistics

Chapter 12: Statistics

Overview

This page provides comprehensive Chapter 12: Statistics - Standard Worksheet - SJMaths. Standard level practice worksheet for Class 9 Statistics.

Standard Level Worksheet

Back to Worksheets
  1. Question 1: The mean of 10 numbers is 20. If 5 is subtracted from every number, what will be the new mean?
    Solution: If each observation is decreased by $k$, the mean is also decreased by $k$. New Mean $= 20 - 5 = 15$.
  2. Question 2: Find the median of the following data: 19, 25, 59, 48, 35, 31, 30, 32, 51.
    Solution: Arrange in ascending order: 19, 25, 30, 31, 32, 35, 48, 51, 59. $n=9$ (odd). Median $= ((n+1)/2)^{th}$ term $= 5^{th}$ term $= 32$.
  3. Question 3: If the mean of $x, x+3, x+6, x+9, x+12$ is 10, find $x$.
    Solution: Sum $= 5x + 30$. Mean $= (5x+30)/5 = x+6$. Given $x+6 = 10 \Rightarrow x = 4$.
  4. Question 4: The points scored by a team in a series of matches are: 17, 2, 7, 27, 15, 5, 14, 8, 10, 24, 48, 10, 8, 7, 18, 28. Find the median.
    Solution: Arrange: 2, 5, 7, 7, 8, 8, 10, 10, 14, 15, 17, 18, 24, 27, 28, 48. $n=16$. Median $= (\text{8th term} + \text{9th term})/2 = (10+14)/2 = 12$.
  5. Question 5: Find the mode of the following distribution: 14, 25, 14, 28, 18, 17, 18, 14, 23, 22, 14, 18.
    Solution: 14 occurs 4 times, 18 occurs 3 times. Mode $= 14$.
  6. Question 6: The mean of 40 observations was 160. It was detected on rechecking that the value 165 was wrongly copied as 125 for computation of mean. Find the correct mean.
    Solution: Incorrect Sum $= 40 \times 160 = 6400$. Correct Sum $= 6400 - 125 + 165 = 6440$. Correct Mean $= 6440 / 40 = 161$.
  7. Question 7: Find the mean of all factors of 24.
    Solution: Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24. Sum $= 60$. Count $= 8$. Mean $= 60/8 = 7.5$.
  8. Question 8: If the median of the data arranged in ascending order: 29, 32, 48, 50, $x$, $x+2$, 72, 78, 84, 95 is 63, find the value of $x$.
    Solution: $n=10$. Median $= (5^{th} + 6^{th})/2 = (x + x+2)/2 = (2x+2)/2 = x+1$. Given $x+1 = 63 \Rightarrow x = 62$.
  9. Question 9: The mean of 5 numbers is 27. If one number is excluded, their mean becomes 25. Find the excluded number.
    Solution: Sum of 5 numbers $= 5 \times 27 = 135$. Sum of 4 numbers $= 4 \times 25 = 100$. Excluded number $= 135 - 100 = 35$.
  10. Question 10: Find the class mark of the class 130 - 150.
    Solution: Class mark $= (130 + 150) / 2 = 280 / 2 = 140$.
Previous Worksheet Next Worksheet