 Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum  MENU          Session 9, Part C:
Investigating Variation in Estimates

In This Part: Using a Stem and Leaf Plot | Judging the Quality of Estimates | Intervals
Describing Intervals | Probabilities

These six intervals provide a description of how widely the estimates vary from sample to sample, and how close the estimates are to the actual value of 500: Note 6  Interval Interval Range Interval Radius Proportion of Estimates in Interval        350-650 300 150 100/100 375-625 250 125 98/100 400-600 200 100 94/100 425-575 150 75 84/100 450-550 100 50 69/100 475-525 50 25 37/100 The interval from 350 to 650 is the largest interval in the table above; its interval range is 300. This tells us two things:

 • All (100/100) of the estimates are between 350 and 650, a range of 300. • These estimates fall within 150 (the interval radius) of 500.

The interval 475 to 525 is the smallest interval in the table. This tells us two things:

 • Fewer than half (37/100) of the estimates are between 475 and 525, a range of 50. • These estimates fall within 25 (the interval radius) of 500. Problem C5 a. Explain why it is useful for the proportion of estimates in an interval to be high. b. Explain why it is useful for the interval range to be small. c. What happens to the proportion of estimates in the interval as the interval range decreases?   Session 9: Index | Notes | Solutions | Video

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