1. Sampling variability & the effect of spread of population

2. The scenario Intermediate School Year 7 & 8 Middle School Year 7 – 10  An intermediate school wants to purchase new furniture for their students, based on the median height of students in years 7 and 8.  A teacher takes a sample of 30 intermediate students from C@S to make an estimate of the population median  A middle school wants to purchase new furniture for their students, based on the median height of middle school students.  A teacher takes a sample of 30 middle school students from C@S to make an estimate of the population median

3. Which teacher is likely to get a better estimate of the students heights? HANDOUTSampling variability WHY?

4. Conclusions  Increased spread in the population for a given sample size produces more variability in the median  As the spread increases, we can be less certain about the population median  As the spread increases, the range of the sample medians increases

5. The big point  We can cope with the uncertainty of predicting the population median by giving a possible range of values, that is, an interval within which the population parameter probably lies  What would this range of values depend on?  Can we predict this interval?