Statistics and Probability

Grade 8: independent vs. dependent events and data measures.

14 questions, free, marked as you go with a worked explanation on every one.

What this covers

The questions

  1. A bag has 3 red and 7 blue marbles. You draw one, put it back, then draw again. What is the probability (as a percent) both are red?
  2. Drawing a marble from a bag, replacing it, then drawing again. These events are:
  3. Drawing a marble from a bag and NOT replacing it before drawing again. These events are:
  4. Find the mean of: 12, 15, 18, 9, 21.
  5. A data set is: 5, 7, 7, 9, 12. Find the mode.
  6. A bag has 4 yellow and 6 green marbles. You draw one, do NOT replace it, then draw again. What is the probability (as a fraction) both are yellow?
  7. Find the range of this data set: 14, 22, 9, 31, 18
  8. Rolling two separate dice, the events "first die shows 6" and "second die shows 6" are:
  9. Find the median of: 4, 15, 8, 23, 11, 19
  10. A class of 24 students has a mean test score of 72. Two students who scored 40 and 50 transfer out of the class. What is the mean score of the 22 students who remain, rounded to one decimal place?
  11. A class of 5 students scores 72, 78, 81 and 85 on a test, and one more student still needs to be scored. If the mean of all 5 scores is 80, what did the fifth student score?
  12. A data set has one unusually large outlier. Which measure of central tendency is most affected by it?
  13. In a class, 3 students are 140 cm tall, 12 students are 150 cm tall, and 5 students are 160 cm tall. What is the mean height of the 20 students, in centimetres?
  14. Class A's test scores have a range of 6 points. Class B's test scores have a range of 24 points. Which class's scores are more consistent?

Answer these free